JP2013042298A - Imaging apparatus and flicker generation frequency detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus and flicker generation frequency detection method capable of excellently preventing the generation of a flicker.SOLUTION: An imaging apparatus 1 includes: an imaging part 7 for performing a flicker detection accumulation to detect the frequency of a power source to be supplied to a light source that causes the generation of a flicker in a captured image and a normal imaging accumulation other than the flicker detection accumulation; a frequency detection part 10 for detecting a frequency on the basis of the accumulation result of the flicker detection accumulation in the imaging part 7; a storage part 9 for storing first information p1 indicating the relation of first exposure control where the control range of an accumulation time TV is a first range and second information p50, p60 indicating the relation of second exposure control where the control range of the accumulation time TV is a second range at a lower speed compared with that of the first range; and a control part 10 for performing exposure control on the basis of the first information p1 stored in the storage part 9 when the flicker detection accumulation is performed and performing exposure control on the basis of the second information p50, p60 stored in the storage part 9 when the imaging accumulation is performed.

Description

  The present invention relates to an imaging apparatus and a flicker generation frequency detection method.

  A digital single-lens reflex camera has a function called a so-called live view in which a quick return mirror is constantly raised and images are continuously output to a display device by an image sensor. When this live view is performed, flicker may occur in an image displayed on the display device due to the influence of the fluctuation of the light source caused by the frequency of the power source of the light source, depending on the accumulation time of the image sensor. Conventionally, various countermeasures have been taken as countermeasures against these flickers (see, for example, Patent Document 1).

JP 2002-94878 A

  An object of the present invention is to provide an imaging apparatus and a flicker occurrence frequency detection method capable of satisfactorily preventing the occurrence of flicker.

The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected and demonstrated, it is not limited to this.
According to the first aspect of the present invention, flicker detection accumulation for detecting the frequency of a power source supplied to a light source that causes flicker in a photographed image, and normal imaging other than the flicker detection accumulation An imaging unit (7) capable of accumulating, a frequency detection unit (10) for detecting the frequency based on the accumulation result of the flicker detection accumulation of the imaging unit (7), and an accumulation time (TV) The first information (P1) indicating the relationship of the first exposure control in which the control range is the first range, and the control range of the accumulation time (TV) is the second speed lower than the first range. The storage unit (9) storing the second information (P50, P60) indicating the relationship of the second exposure control, which is the range, and the storage unit (9) store the flicker detection accumulation. Exposure based on the first information (P1) And a control unit (10) that performs exposure control based on the second information (P50, P60) stored in the storage unit (9) during the accumulation for imaging. An imaging device (1) characterized by
The invention according to claim 2 is the imaging apparatus (1) according to claim 1, wherein a frame rate at the time of accumulation for imaging is slower than a frame rate at the time of accumulation for flicker detection. It is the imaging device (1) characterized.
A third aspect of the present invention is the imaging apparatus (1) according to the first or second aspect, wherein the lower limit of the accumulation time (TV) in the first range is set to be higher than that during normal image capturing. An imaging device (1) characterized by
The invention according to claim 4 is the imaging apparatus (1) according to claim 3, wherein the first information (P1) and the second information (stored in the storage unit (9)). P50, P60) is a correspondence between imaging sensitivity (ISO), values (BV-AV, BV-AV + 1/3) corresponding to light reaching the imaging unit (7), and the storage time (TV). The imaging device (1) is characterized by being a program diagram.
According to the fifth aspect of the present invention, the flicker detection accumulation for detecting the frequency of the power source supplied to the light source that causes flicker in the photographed image and the normal other than the flicker detection accumulation An image pickup unit (7) capable of image pickup, a frequency detection unit (10) for detecting the frequency based on the flicker detection accumulation result of the image pickup unit (7), and an accumulation time (TV ) Of the first information (P1) indicating the relationship of the first exposure control, which is the first range, and the control range of the storage time (TV) is lower than the first range. In the imaging device (1), the storage unit (9) storing the second information (P50, P60) indicating the relationship of the second exposure control that is the range of 2 in the flicker detection storage Stored in the storage unit (9) The exposure control is performed based on the first information (P1), and the exposure control is performed based on the second information (P50, P60) stored in the storage unit (9) during the accumulation for imaging. Performing a flicker generation frequency detection method.

  Note that the configuration described with reference numerals may be modified as appropriate, and at least a part of the configuration may be replaced with another component.

  According to the present invention, it is possible to provide an imaging apparatus and a flicker generation frequency detection method that can satisfactorily prevent occurrence of flicker.

It is a block diagram of a camera to which an embodiment of the present invention is applied. It is a flowchart which shows the basic operation | movement of a camera. It is a figure explaining the accumulation | storage method in an area sensor. It is a general | schematic flow of a flicker frequency detection process. It is a P diagram for flicker frequency detection. It is a figure which shows the relationship between an imaging output and the number of frames. It is a P diagram for live view for 50 Hz. It is a P diagram for live view for 60 Hz.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a configuration diagram of a digital single-lens reflex camera 100 of the present embodiment.
The camera 100 includes a camera body 1 and a lens unit 2.
Here, the lens unit 2 is attached to the camera body 1 so as to be replaceable, and includes an imaging optical system 3 and an aperture 4.
The imaging optical system 3 includes a plurality of lens groups (only two lenses are shown in the figure). The plurality of lens groups includes a zoom lens group and a focus lens group.
The diaphragm 4 limits the amount of light flux that passes through the imaging optical system 3 and reaches an imaging device 7 (described later) provided in the camera body 1.

The camera body 1 includes a quick return mirror 5, a focal plane shutter 6, an image sensor 7 that photoelectrically converts a subject image, and images (including moving images (including live view images) and still images) captured by the image sensor 7. And a display unit 8 for displaying.
In addition, the camera body 1 includes a finder optical system 20, an area sensor 16 that performs photoelectric conversion of a subject image, a control unit 10 that performs calculations to control them, and a storage unit 9 that stores control information.
The quick return mirror 5, the focal plane shutter 6, and the image sensor 7 are arranged along the optical axis OA of the imaging optical system 3, and the finder optical system 20 is arranged in the upper region of the quick return mirror 5.

When the photographer observes the scene through the finder optical system 20, that is, other than still image shooting and moving image shooting (including live view), the quick return mirror 5 moves from the imaging optical system 3 to the image sensor 7. The light beam that intersects the imaging optical path and passes through the imaging optical system 3 is reflected upward and guided to the finder optical system 20 (the position of the solid line).
On the other hand, at the time of still image shooting and moving image shooting (including live view), the quick return mirror 5 is flipped upward, and the light beam that has passed through the imaging optical system 3 is guided to the focal plane shutter 6 and the image sensor 7 to capture the image. Image data of the subject can be generated based on the image pickup signal of the element 7 (dotted line position).

The finder optical system 20 includes a finder screen 11, a penta roof prism 12, and an eyepiece lens 14.
The light beam from the subject passes through the imaging optical system 3 and the diaphragm 4 of the camera 100 and is then reflected upward by the quick return mirror 5. Then, the light beam from the subject reflected by the quick return mirror 5 forms an image on the finder screen 11 disposed on a surface optically equivalent to the image sensor 7. The luminous flux of the formed subject image passes through the penta roof prism 12, passes through the eyepiece lens 14, and then travels to the finder 17.
A part of the light beam that has passed through the penta roof prism 12 passes through the area sensor re-imaging optical system 13 and forms an image on the area sensor 16.

  The area sensor 16 is composed of a 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 for each region in order to calculate an exposure value at the time of photographing. This output signal is also used to detect the frequency of the AC power supply (hereinafter referred to as flicker frequency) supplied to the light source included in the object scene, which causes flicker in the captured image, which will be described later. The

The imaging device 7 is provided on the optical axis OA of the camera body 1 at a position that is a planned focal plane of the imaging optical system 3, and the focal plane shutter 6 is provided on the front surface thereof.
The imaging device 7 is a device in which a plurality of photoelectric conversion devices are two-dimensionally arranged, and can be constituted by a two-dimensional CCD sensor, a CMOS sensor, or the like.
The electrical imaging signal photoelectrically converted by the imaging device 7 is subjected to image processing by the control unit 10 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 camera body 1 also includes an operation unit 21. The operation unit 21 includes a release switch, a zoom button, and an input switch for the photographer to set various operation modes of the camera body 1.

When the user of the camera 100 presses the release switch 21, the camera 100 starts a shooting operation.
In the photographing operation, first, the quick return mirror 5 jumps upward (dotted line). The camera 100 opens the shutter curtain of the focal plane shutter 6, receives the light beam with the image sensor 7, and outputs an image signal.
The imaging signal is processed by the control unit 10 in the same manner as the output of the area sensor 16. Then, the captured image is displayed on the display unit 8.

In the live view mode (including moving image shooting), the camera 100 flips the quick return mirror 5 upward.
Then, the camera 100 opens the focal plane shutter 6 and the image sensor 7 receives the light beam from the subject. The output of the image sensor 7 is processed by the control unit 10 and displayed as a through image on the display unit 8.

  Next, the flow of processing in this embodiment will be described. FIG. 2 is a flowchart showing the basic operation of the camera 100 from the state in which the camera 100 of FIG.

The camera 100 that is turned on is in a state in which the quick return mirror 5 is in the mirror-down state, and the subject light incident from the imaging optical system 3 is guided to the area sensor 16.
In S201, the area sensor 16 accumulates subject light.
The accumulation here is an accumulation for setting an exposure condition at the time of still image shooting and an exposure condition for flicker frequency detection in S205 described later. Further, the first exposure condition at the time of live view in S207, which will be described later, is also set based on the accumulation result here. The accumulation result is output as a signal and processed by the control unit 10.

FIG. 3 is a diagram for explaining a storage method in the area sensor 16 in S201. In the area sensor 16, the object scene is divided into blocks. In the present embodiment, the object field of the area sensor 16 is divided into 5 × 5 blocks as shown.
The output of each block is expressed as Y [i] [j] using coordinates (i, j), and takes a value of 0 to 1023 in each block. Then, the area sensor 16 transmits the output of each block to the control unit 10.

In S <b> 202, the camera 100 calculates the luminance value of 25 blocks from the signal output of the area sensor 16 in the control unit 10.
The luminance value is calculated as follows.
BV [i] [j] = Log2 (Y [i] [j]) + CONST (Formula 1)
In Expression 1, Log2 () is a function that returns the logarithm of the argument with base 2.
CONST is a term for normalizing the accumulation time, sensitivity, and brightness of the photographing lens when the area sensor 16 is accumulated. The processing of Formula 1 is performed for all 25 combinations of i and j.

  In S203, the camera 100 determines whether or not the user has started a live view. If the live view is not started (S203, NO), the processing from S201 to S202 is repeated.

  When the camera 100 determines that the user has started the live view operation (S203, YES), the quick return mirror 5 is flipped up in S204, the focal plane shutter 6 is opened, and the image pickup device 7 takes an image. Make it possible.

(Flicker frequency detection)
Next, the camera 100 detects the flicker frequency in S205.
FIG. 4 is an outline flow of the flicker frequency detection process in S205.

As shown in FIG. 4, in the flicker frequency detection process, the control unit 10 obtains an accumulation condition for flicker frequency detection in S301. In the present embodiment, the calculation of the flicker frequency detection accumulation condition is described with respect to the example performed in S301. However, the present invention is not limited to this, and may be performed before the start of the live view, for example.
In S301, the control unit 10 first obtains the area having the maximum luminance from the areas measured in S202.
BV25MAX = MAX (BV [i] [j]) (Formula 2)
In Expression 2, MAX () is a function that returns the maximum value of the argument array.

  Based on the calculated BV25MAX and the aperture value AV of the aperture 4 of the photographing lens 2 (BV-AV), the accumulation time shutter speed and the ISO sensitivity are calculated from the flicker frequency detection P diagram P1 shown in FIG. This P diagram is a P diagram in which BV25MAX is not saturated (out-of-white) and is stored in the storage unit 9.

Here, the reason why the luminance BV25MAX in the area with the highest luminance is not saturated (out-of-white) is as follows.
This is because there is a possibility that a part of the image sensor 7 is saturated with a proper exposure during normal live view display (exposure so that the display device has a proper brightness). However, the cause of flicker is generally a light source such as a fluorescent lamp, and detecting the flicker frequency means detecting blinking of the light source.
The light source is often brightest on the screen, and it is highly likely that the bright light source will saturate (out-of-white) under normal exposure conditions. I cannot get data on the flicker frequency.

  Therefore, in the present embodiment, the object field is measured by the area sensor 16 before the flicker frequency is detected, and the maximum luminance portion of the screen is not saturated when the image sensor 7 used for detecting the flicker frequency is driven. Perform exposure control. Thereby, the flicker frequency can be detected in a state where the output is not saturated.

(High frame rate)
Next, accumulation for flicker frequency detection is performed in S302. This accumulation is performed at a high frame rate. The high-speed frame rate in the present embodiment is a frame rate that is sufficiently high with respect to a flicker frequency such as an expected disillusion frequency of 100 Hz or 120 Hz (corresponding to a power source of 50 Hz and 60 Hz), preferably 700 fps or more. More preferably, it is 800 fps to 1200 fps.

  In the case of a high-speed frame rate, since the shooting operation period (accumulation time, shutter time) of one frame is very short, the brightness of the surrounding environment during the shooting operation period of one frame is almost constant even under a fluorescent lamp. . Therefore, no banded light and dark appear in the frame image. In such a continuous image at a high frame rate, light and dark due to blinking of a fluorescent lamp appear as light and dark in successive frames. That is, in the case of a high frame rate, it is possible to grasp the cycle of the fluorescent lamp blinking by plotting the luminance of each frame.

(At high shutter speed)
In order to accurately detect the fluctuation of the light source, it is preferable to detect the instantaneous light quantity at a high shutter speed. Further, since the minimum shutter speed (TV) is 1 / frame rate, the shutter speed is also high to achieve a high frame rate. For this reason, when the image sensor 7 is driven to detect the flicker frequency, an exposure control P diagram for detecting the flicker frequency, which is provided separately from the exposure control P diagram for normal shooting, is used. Use.

FIG. 5 shows an exposure control P diagram when detecting the flicker frequency. This P diagram is different from the P diagram in the case of normal photographing, and corresponds to a frame rate of 800 fps, and the minimum shutter speed is 1/800, which is high speed.
As described above, since the exposure control P diagram is provided separately for shooting at the time of live view, it is possible to perform imaging specialized for flicker frequency detection in the imaging unit 7, regardless of the exposure control conditions at the time of live view. Therefore, it is possible to detect the flicker frequency with high accuracy.

  This accumulation in S303 is repeated until a predetermined number of times (80 times in the present embodiment) is exceeded. This is because when a plurality of light sources are present in the object scene or when the luminance of the light sources changes, the frequency may not be detected accurately with a single detection result.

(Binarization processing)
FIG. 6 shows a result of accumulation of the image sensor 7 performed for flicker frequency detection. The vertical axis is an output value corresponding to the luminance of the object scene.
In S303, when the number of accumulation exceeds a predetermined number (80 in the present embodiment) (S303, Yes), in S304, the acquired output of the image sensor 7 is binarized.
Binarization is performed as follows.
First, the average value of the imaging output accumulated at the nth time in the accumulation of 1 to 80 times is defined as YMean [n]. And the average is calculated | required.
AveYMean = AVERAGE (YMean [n])
AVERAGE () is a function that returns the average value of the argument array. In FIG. 6, AveMean is indicated by a dotted line.

Next, the output of each frame is binarized. Binarization is performed based on the following equation.
If YMean [n]> AveYMean, FLBIT [n] = 1
If YMean [n] ≦ AveYMean, FLBIT [n] = 0

The result of the binarization process is indicated by a two-dot chain line on the graph of FIG.
As shown in FIG. 6, when binarization is performed, FLBIT [n] = 1 continues multiple times (L1), then FLBIT [n] = 0 continues multiple times (L0), and FLBIT [n] = 1 FLBIT = 1 (L1) and FLBIT = 0 (L0) are repeated a plurality of times.

The number of frames each including one set each of a plurality of consecutive FLBIT = 1 (L1) and a plurality of consecutive FLBIT = 0 (L0) is counted.
That is, as shown in FIG. 6, the first time (T1) counts the number of frames from the first 1 when FLBIT rises from 0 to 1 to the last 0 before the next rise from 0 to 1.
The second time (T2) overlaps with the half of the first count area (T1), and the number of frames from the first 0 when falling from 1 to 0 to the last 1 before falling from 1 to 0 next. count.
The third time (T3) overlaps with half of the second count area (T2), and the number of frames from the first 1 when rising from 0 to 1 to the last 0 when rising from 0 to 1 next. count.

The time obtained by multiplying the number of frames each including one continuous set L1 and one continuous set L0 by one frame rate is ½ period of the flicker frequency (1 of the blinking of the light source). Period).
The overlapping count area corresponds to a quarter cycle of the flicker frequency (a half cycle of the light source blinking).

  In this way, by overlapping the count region T, a plurality of samplings can be performed in a short time.

However, the present invention is not limited to this. For the first time, the number of frames from the first 1 when FLBIT rises from 0 to 1 to the last 0 before rising from 0 to 1 is counted. In the second time, the number of frames from the first 1 when FLBIT rises from 0 to 1 to the last 0 before rising from 0 to 1 can be counted without overlapping. Good.
Alternatively, the first time may start from the first 0 when FLBIT falls from 1 to 0.

  For example, AveYMean may be larger than the center value of the actual output due to sampling. As a result, the number of consecutive FLBIT = 1 decreases, and the number of consecutive FLBIT = 0 increases accordingly. However, in this embodiment, since the number of frames included in one set of continuous 1 and continuous 0 is counted, even if the value of AveYMean / 2 is deviated from the center, it is substantially correct as a whole. The number of frames in one cycle can be counted.

Here, the blinking of the light source occurs at 100 Hz when the power source is 50 Hz, for example, and 120 Hz when the power source is 60 Hz.
The count area (T1, T2, T3...) Is one count area. For example, when eight frames are detected, if the frame rate is 800 fps, the one count area is 1/100 second. In this case, since the blinking of the light source is 100 Hz, the power source is considered to be 50 Hz.

  For example, when the number of detected frames in one cycle is 7 (the number of frames is an integer, and the time corresponding to the number of frames is determined based on which of the light source blinking cycles is closer), the frame rate is 800 fps. Then, one cycle is 1/120 second. In this case, since the blinking of the light source is 120 Hz, the power source is considered to be 60 Hz.

Therefore, ThHz is set to about 7, for example, and the number of frames T (n) included in each cycle is
If T [n]> ThHz, it is determined as 50 Hz,
If T [n] ≦ ThHz, it is determined as 60 Hz.

(Flicker frequency judgment)
In all T [n], it is determined whether it is 50 Hz or 60 Hz, and the larger one of the determined numbers of 50 Hz and 60 Hz is adopted to obtain the flicker frequency.

Here, when detecting whether the flicker frequency is 50 Hz or 60 Hz, there is a case where the detection cannot be performed accurately because it is too dark. In addition, the number of times determined to be 50 Hz may be the same as the number of times determined to be 60 Hz.
As described above, when it is not possible to determine whether the frequency is 50 Hz or 60 Hz, the control unit 10 is equal to or less than one frame rate at the time of image capturing of 50 Hz or 60 Hz, and is 1/2 cycle of the flicker frequency ( The longest of the integer multiples of 1/100, 1/120) (1/100, 2/10, 3/100, 4/100 or 1/120, 2/120, 3/100, 4/120) However, the flicker frequency having a long time is determined as the flicker frequency causing the occurrence of flicker.
In other words, in the present embodiment, if the frame rate at the time of image capture is 24, for example, it is equal to or less than one frame rate (1/24 = 0.0416) and is a half cycle of a flicker frequency of 50 Hz ( Among those that are integer multiples of 1/100), the longest is 4/100 = 0.04.
It is equal to or less than one frame rate (1/24 = 0.0416), and is an integral multiple of 1/2 period (1/120) of the flicker frequency of 60 Hz (1/120, 2/120 = 0.167, 4 /120=0.0333), the longest is 4/120 = 0.0333. Therefore, in this case, 50 Hz is determined as the flicker frequency.
This is because it is inevitable that the shutter time is 1 / frame rate in the exposure control, and the flicker including the longest one among the integral multiples of ½ period of the flicker frequency. This is because the use of the frequency makes the flicker less noticeable because the shutter speed is low.

Next, returning to FIG. 2, the image sensor for live view display is stored in S207.
At this time, at the time of the first live view, the following processing is performed in order to determine the storage condition of the image sensor for live view using the output of the area sensor 16 stored in S201.

BVMean = AVERAGE (BV [i] [j]) (Formula 3)
In Equation 3, AVERAGE () is a function that returns the average value of the argument array.
Based on the calculated BVMean and the aperture AV value of the photographic lens, the storage time and sensitivity are calculated using a P diagram for live view. At this time, based on the flicker frequency detection result in S205, it is determined which of the P diagram for live view for 50 Hz in FIG. 7 or the P diagram for live view for 60 Hz in FIG. . These P diagrams are also stored in the storage unit 9.

As described above, when the flicker frequency cannot be detected in S205, the exposure control value is determined using the 50 Hz P diagram of FIG.
In S208, the brightness value for the second and subsequent times is calculated from the result of the live view imaging accumulation detected in S207 based on the selected P diagram.

The luminance value is calculated by the following formula.
BVSz = Log2 (AVERAGE (YSz [x] [y])) + SzCONST
... (Formula 4)
In Expression 4, YSz [x] [y] is an output at the coordinates (X, Y) of the image sensor 7. SzCONST is a term for normalizing the accumulation time, sensitivity, and brightness of the photographing lens when the image sensor 7 is accumulated.

Here, when it is determined that the flicker frequency of the light source is 50 Hz, the shutter time is 1/25, 1/50, and 1/100 as shown in the P diagram P50 of FIG. , Luminance variation is eliminated and flicker is prevented. That is, when the shutter speed is 1/100, the light source is accumulated for one blink (one peak), and when the shutter time is 1/50, the light source is blinked twice (two peaks). ), And when the shutter speed is 1/25, the light source is accumulated for four blinks (four peaks).
Although not included in the P diagram of FIG. 7, the light source may be accumulated for three blinks (three peaks) at a shutter time of 1/33. As described above, since accumulation is performed for an integral multiple of blinking, a difference in image brightness due to blinking of the light source does not occur between the accumulated images, and flicker is prevented.

Further, when the frequency of the light source is 60 Hz, the shutter time is 1/30, 1/60, and 1/120 as shown in the P diagram of FIG. And flicker is prevented. That is, when the shutter speed is 1/120, the light source is accumulated for one blink (one peak), and when the shutter time is 1/60, the light source is blinked twice (two peaks). ), And when the shutter speed is 1/30, the light source is accumulated for four blinks (four peaks).
Although not included in the P diagram of FIG. 8, the light source may be accumulated for three blinks (three peaks) at a shutter speed of 1/45. As described above, even at 60 Hz, accumulation is performed for an integral multiple of blinking. Therefore, a difference in image brightness due to blinking of the light source does not occur between the accumulated images, and flicker is prevented.

  At higher speeds (indicated by dotted lines in FIGS. 7 and 8), flicker may occur. In this case, the diaphragm 4 may be squeezed to reduce the shutter speed, and when the diaphragm 4 is squeezed, if abnormal noise is annoying, it can be left as it is.

In step S209, the output image of the image sensor 7 accumulated in step S207 is displayed on the display unit 8.
If the release switch 21 is not pressed in S210, shooting is not performed, and the live view state from S207 to S209 is continued unless the live view is terminated in S212. When the release switch 21 is pressed in S210, the image sensor 7 for recording a still image is stored in S211. A known method is used for the accumulation condition of the image sensor for still image recording.

As described above, this embodiment has the following effects.
(1) The object field is measured by the area sensor 16 before the flicker frequency is detected, and exposure control is performed so that the maximum luminance portion of the screen is not saturated when the image sensor 7 used for detecting the flicker frequency is driven. Like that. Thereby, the flicker frequency can be detected in a state where the output is not saturated. Since the light source does not fly out, it is possible to detect blinking of the light source and to obtain data relating to the frequency of the light source satisfactorily.

(2) In the present embodiment, accumulation during flicker frequency detection is performed at a high frame rate. The high-speed frame rate is a sufficiently high rate with respect to the frequency of the light source, such as 100 Hz or 120 Hz (corresponding to 50 Hz and 60 Hz power supplies).
In the case of a high-speed frame rate, the brightness of the surrounding environment during the shooting operation period of one frame is almost constant even under a fluorescent lamp. Therefore, no banded light and dark appear in the frame image. In such a continuous image at a high frame rate, light and dark due to blinking of a fluorescent lamp appear as light and dark in a continuous frame. That is, in the case of a high frame rate, it is possible to grasp the cycle of the fluorescent lamp blinking by plotting the luminance of each frame.

(3) In the present embodiment, the shutter speed is high in response to the high frame rate. For this reason, when the image sensor is driven to detect the flicker frequency, an exposure control P diagram for detecting flicker frequency is provided separately from the exposure control P diagram for shooting in live view. Is used.
As described above, since the exposure control P diagram is provided separately from the shooting for live view, it is possible to perform imaging specialized for flicker frequency detection, and the accuracy is high regardless of the exposure control conditions during live view. Flicker frequency detection becomes possible.

(4) In this embodiment, accumulation for detecting the flicker frequency is performed a plurality of times until the predetermined number of times is reached. Therefore, even when there are a plurality of light sources in the field or when the light sources fluctuate, it is possible to detect the flicker frequency with high accuracy.

(5) After binarization, when measuring the blinking frequency of the light source, one set each includes a plurality of consecutive FLBIT = 1 (L1) and a plurality of consecutive FLBIT = 0 (L0) Count the number of frames partially overlapped.
For example, when AveYMean is larger than the center value of the actual output, the number of consecutive FLBIT = 1 is decreased, and the number of consecutive FLBIT = 0 is increased accordingly.
However, in this embodiment, since the number of frames included in one set of continuous 1 and continuous 0 is counted, even if the value of AveYMean / 2 is deviated from the center, it is substantially correct as a whole. The number of frames in one cycle can be counted.
Further, by overlapping the count areas, a plurality of samplings can be determined in a short time.

(6) When it is not possible to determine whether the frequency is 50 Hz or 60 Hz, the control unit is equal to or less than one of the frame rate at the time of image capturing, which is 50 Hz or 60 Hz, and is an integral multiple of 1/2 cycle of the flicker frequency. Of these, the flicker frequency with the longest time is determined as the flicker frequency causing the occurrence of flicker.
For this reason, since the accumulation time is a low shutter speed, flicker is less noticeable.

(7) When the flicker frequency of the light source is determined to be 50 Hz, the shutter time is 1/25, 1/50, and 1/100, which is an integral multiple of a half cycle of the light source, and there is no variation in luminance. Is prevented. Further, when the frequency of the light source is 60 Hz, the shutter time is 1/30, 1/60, and 1/120, so that it becomes an integral multiple of the half cycle of the light source, there is no variation in luminance, and flicker is prevented.

The present invention is not limited to the above-described embodiment, and various modifications and changes as described below are possible, and these are also within the scope of the present invention.
In the present embodiment, a single lens reflex camera having a photometric sensor in addition to the image sensor has been described. However, the present invention is not limited to this, and only an image sensor such as a compact camera may be used. In that case, the process of S201 is performed by the image sensor.
In addition, although embodiment and a deformation | transformation form can also be used in combination as appropriate, detailed description is abbreviate | omitted. Further, the present invention is not limited to the embodiment described above.

  1: camera body, 2: lens unit, 3: imaging optical system, 7: imaging element, 9: storage unit, 10: control unit, 16: area sensor, 100: camera

Claims (5)

An image pickup unit capable of accumulating for detecting flicker for detecting a frequency of a power source supplied to a light source that causes flicker in a photographed image, and capable of accumulating for normal imaging other than the flicker detecting accumulation; ,
A frequency detection unit for detecting the frequency based on the accumulation result of the flicker detection accumulation of the imaging unit;
The first information indicating the relationship of the first exposure control in which the control range of the accumulation time is the first range, and the control range of the accumulation time is the second range that is slower than the first range. A storage unit storing second information indicating a relationship of the second exposure control;
During the flicker detection accumulation, exposure control is performed based on the first information stored in the storage unit,
A controller that performs exposure control based on the second information stored in the storage unit during the imaging accumulation;
An imaging apparatus comprising: The imaging apparatus according to claim 1,
The frame rate at the time of accumulation for imaging is slower than the frame rate at the time of accumulation for flicker detection;
An imaging apparatus characterized by the above. The imaging apparatus according to claim 1 or 2,
The lower limit of the accumulation time in the first range is set to be higher than that during normal image capturing;
An imaging apparatus characterized by the above. The imaging apparatus according to claim 3,
The first information and the second information stored in the storage unit are program diagrams representing correspondence between imaging sensitivity, a value corresponding to light reaching the imaging unit, and the accumulation time. There is,
An imaging apparatus characterized by the above. Image capturing unit capable of accumulating for detecting flicker for detecting the frequency of a power source supplied to a light source that causes flicker in a captured image, and normal image capturing other than the flicker detecting accumulation When,
A frequency detection unit for detecting the frequency based on the accumulation result of the flicker detection accumulation of the imaging unit;
The first information indicating the relationship of the first exposure control in which the control range of the accumulation time is the first range, and
A storage unit storing second information indicating a relationship of second exposure control in which a control range of the accumulation time is a second range that is slower than the first range;
In an imaging apparatus comprising:
During the flicker detection accumulation, exposure control is performed based on the first information stored in the storage unit,
A flicker occurrence frequency detection method, wherein exposure control is performed based on the second information stored in the storage unit during the imaging accumulation.

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