JP2009206569A - Imaging apparatus and flicker correction method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus which is capable of performing flicker correction in a short time without spoiling the quality of an image. <P>SOLUTION: In response to detection of flicker, an image processing IC 106 calculates a phase difference α being a time from a zero point of a flicker waveform to an exposure start timing in the first line of the zeroth field. The image processing IC 106 calculates a correction amount Hn for correction of image data from an imaging device per line on the basis of the calculated phase difference α, a flicker period and an exposure time T. The image processing IC 106 outputs image data corrected per line by using the correction amount Hn, as a field image. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging apparatus having an imaging element in which a plurality of light receiving units are arranged, and a flicker correction method thereof.

  In recent years, in a video camera, the number of pixels is increased and the speed is increased, and a CMOS sensor is used as an imaging element. As a CMOS sensor, from the viewpoint of the area of a photodiode, a floating diffusion (hereinafter abbreviated as FD) amplifier is not provided in every pixel, and one column readout type that exists in each column is mainly used in video cameras and the like. is there.

  In such a column readout type CMOS sensor, exposure is performed until readout is started for each line. Therefore, when exposure is started for all pixels at the same timing and the pixels are read out, the luminance level differs for each line. For this reason, a rolling shutter function for performing exposure by shifting the exposure timing at regular intervals for each line is adopted.

However, even in a video camera using a CMOS sensor having the above function, when a flicker phenomenon such as a fluorescent lamp or a tungsten light bulb occurs due to AC fluctuation of the commercial power supply frequency, the exposure amount changes for each line. For this reason, in one field image, images having different horizontal stripe luminance levels in the vertical direction are generated. On the other hand, conventionally, the luminance level in the vertical direction of an image is detected at any time, a difference is taken between fields, and a flicker component is extracted and corrected (see Patent Document 1).
Japanese Patent No. 0382314

  However, in the above conventional flicker correction method, since flicker components are extracted from a plurality of field images, it takes time for a plurality of fields to be corrected after the flicker phenomenon is detected, and the correction is completed. It took a long time before. In particular, when the subject moves, tracking of correction may not be in time. For this reason, the quality of the image was impaired.

  SUMMARY An advantage of some aspects of the invention is that it provides an imaging apparatus capable of performing flicker correction in a short time without impairing image quality and a flicker correction method thereof.

  In order to achieve the above object, an imaging apparatus according to the present invention includes an imaging device in which a plurality of light receiving units are arranged for each line and for each column, and controls an exposure start timing of the imaging device for each line to thereby set an exposure time A variable electronic shutter means, a flicker detecting means for detecting flicker in which the brightness of the light source fluctuates in accordance with a predetermined frequency, and outputting a level of the detected flicker, and detecting a flicker cycle of the detected flicker And a phase difference calculating means for calculating a phase difference from a time when the flicker level is minimized to an exposure start timing of a predetermined line of the image sensor when the flicker is detected. Based on the detected phase difference, the detected flicker period, and the variable exposure time, the image data from the image sensor is corrected for each line. And means, and outputting the image data corrected for each of the line as the field image.

  The flicker correction method for an image pickup apparatus according to the present invention is a flicker correction method for an image pickup apparatus having an image pickup element in which a plurality of light receiving portions are arranged for each line and for each column, wherein the electronic shutter means starts exposure of the image pickup element. A step of varying the exposure time by controlling the timing for each line, and a step of detecting flicker in which the brightness of the light source fluctuates according to a predetermined frequency and outputting the detected flicker level. And a step of detecting a flicker cycle of the detected flicker, and when the flicker is detected, from a time when the flicker level is minimum to an exposure start timing of a predetermined line of the image sensor. Calculating a phase difference between the calculated phase difference, the detected flicker period, and the variable exposure time. The basis, and correcting the image data from the imaging device for each line, characterized in that a step of outputting the image data corrected for each of the line as the field image.

  According to a first aspect of the present invention, when flicker is detected, the imaging apparatus calculates a phase difference from a time when the flicker level is minimum to an exposure start timing of a predetermined line of the imaging device, and the phase difference, flicker is calculated. Based on the period and exposure time, the image data is corrected for each line. Accordingly, correction data can be determined before image data is output, and flicker correction can be performed in a short time without impairing image quality.

  According to the imaging apparatus of the second aspect, since the correction amount is calculated using the ratio between the exposure amount of the predetermined line and the exposure amount of the line having the largest value, the correction amount can be easily calculated. .

  According to the imaging apparatus of the third aspect, since the luminance level of a part of the subject area is output as the flicker level, the flicker level can be output in a short time with a small amount of data.

  According to the imaging apparatus of the fourth aspect, by counting the number of fields, the same correction data can be used for each predetermined number of fields, and the field image can be easily corrected.

  According to the imaging apparatus of the fifth aspect, the flicker correction can be performed in a shorter time by using the correction amount stored in the table.

  Embodiments of an imaging apparatus and a flicker correction method thereof according to the present invention will be described with reference to the drawings. The imaging device of this embodiment is applied to a video camera device.

[First Embodiment]
FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus according to the first embodiment. The lens unit 100 includes an AF mechanism for converging and focusing a light amount from a subject, a zoom mechanism, and a diaphragm for controlling the light amount. The CMOS sensor 101 is a semiconductor imaging device in which a plurality of light receiving units are arranged for each line and for each column, and mainly converts light of a subject image that has passed through the lens unit 100 into an electrical signal. The sensor control unit 102 is connected to the CPU 109 and mainly performs timing control of the CMOS sensor 101.

  An AFE (analog processing circuit) unit 103 removes noise from the image signal output from the CMOS sensor 101 by a correlated double sampling circuit (CDS), and converts the analog signal to a digital signal by an A / D conversion unit. . In addition, the AFE unit 103 includes an amplifier unit that amplifies the image signal with a predetermined gain in order to obtain a desired level.

  The flicker sensor 104 is used to detect a flicker component from a change in the amount of light of the subject light, and electrically outputs a subject light amount level (flicker level) at an arbitrary frequency. That is, the flicker sensor 104 outputs the subject light amount level in a relatively small arbitrary region (partial region) in the actual image area as needed based on the subject image information of the image processing IC 106. The level conversion unit 105 performs voltage conversion in order to match the electric signal output from the flicker sensor 104 with the I / F of the image processing IC 106.

  The image processing IC 106 is controlled by the CPU 109 and mainly performs image processing such as γ correction, contour enhancement correction, white balance, and flicker correction on the image signal output from the AFE unit 103.

  Next, the flicker correction unit inside the image processing IC 106 will be described. The flicker detection unit 106a detects the presence or absence of a flicker phenomenon in which the brightness of the subject light appears in synchronization with the commercial power supply frequency such as a fluorescent lamp, based on the level change of the signal output from the level conversion unit 105. The phase / period detection unit 106 b records a flicker waveform at the time of flicker detection, and calculates a flicker period and a phase difference between the flicker waveform and the exposure timing of the CMOS sensor 101. The phase / period detection unit 106b corresponds to a period detection unit and a phase difference calculation unit described in the claims. The correction unit 106c records correction data for each line of image data obtained from the phase difference, flicker cycle, and flicker waveform as a table, and actually performs correction using the correction data. The correcting unit 106c corresponds to the correcting unit described in the claims.

  The image conversion unit 107 converts the image data output from the image processing IC 106 into moving image format data recorded in the recording unit 108. The recording unit 108 is a recording medium such as a DVD, a DV tape, or an SD card, and records moving image format data converted by the image conversion unit 107. The CPU 109 controls the entire imaging apparatus.

  The operation of the imaging apparatus having the above configuration will be described. FIG. 2 is a flowchart showing the procedure of flicker correction processing. This process is executed by the image processing IC 106. Here, the subject light that has passed through the lens unit 100 is converted into an electrical signal by the CMOS sensor 101, output as digital image data from the AFE unit 103, and input to the image processing IC 106.

  First, the image processing IC 106 sets the sampling frequency of the flicker sensor 104 to 10 kHz, and measures the flicker signal input via the level conversion unit 105 (step S1). Then, based on the measured flicker signal, the image processing IC 106 detects the presence or absence of flicker (step S2). As described above, the flicker sensor 104 electrically outputs a subject light amount level at an arbitrary frequency. Based on the subject image information of the image processing IC 106, the flicker sensor 104 is a relatively small arbitrary light amount in an actual image area. The level of the subject light amount in the area is output as needed.

  When the flicker phenomenon does not occur, the flicker signal has a constant or non-periodic variation. In this case, it is determined in step S2 that there is no flicker. Then, the image processing IC 106 outputs image data by a normal imaging operation (step S11). Thereafter, the image processing IC 106 returns to the process of step S1. On the other hand, when the flicker phenomenon has occurred, the image processing IC 106 performs the processing after step S3.

  FIG. 3 is a diagram showing a temporal change of the flicker signal when the flicker phenomenon occurs. The flicker waveform 300 of the flicker signal indicated by the curve repeats light and dark with a period synchronized with a commercial power supply frequency such as a fluorescent lamp. In the present embodiment, the power source frequency is 50 Hz, and a light source such as a fluorescent lamp connected to a 50 Hz AC power source repeats the light and darkness represented by a COS curve with a period of 100 Hz as shown in FIG.

  The flicker sensor 104 outputs a subject light amount level to the image processing IC 106 at a sampling period of 10 kHz. The flicker detection unit 106a in the image processing IC 106 holds the level of the subject light amount at each sampling timing. That is, the flicker detection unit 106a records the light amount level of the subject light at a certain timing as Yx and the levels at the next sampling as Yx + 1, Yx + 2,..., Yx + 100,.

  The level converter 105 amplifies or attenuates so that the maximum value of the light amount level becomes the maximum voltage of the input unit of the image processing IC 106 and the minimum value of the light amount level becomes “0” [V] as the minimum voltage. And offset processing.

  The flicker detection unit 106a in the image processing IC 106 performs matching as to whether or not the held light amount level Y has a COS curve characteristic with a period of 100 Hz. Specifically, when the interval between the maximum point and the next maximum point is about 10 [ms] (100 sampling points or 100 Hz), the flicker detection unit 106a has a cycle of 100 Hz. It is determined that the light amount level Y is fluctuating.

  Further, a function y = COS (t) is held in the image processing IC 106, and the flicker detection unit 106a performs matching between the light amount level Y of each point and a COS curve having a period of 100 Hz. That is, when the light amount level Y is equal to or higher than a certain level and similar to the COS curve, the flicker detection unit 106a determines that flicker occurs due to the cycle of the commercial power supply of 50 Hz.

  If the interval between the maximum point and the next maximum point is about 8.333 [ms], the flicker detection unit 106a determines that the light amount level Y fluctuates at a cycle of 120 Hz. . Since this is a flicker cycle in the 60 Hz band, the flicker detection unit 106a similarly performs matching between the light amount level Y and the COS curve, and determines the presence or absence of flicker at 120 Hz. The identification of the commercial power supply in the 50 Hz band or 60 Hz band may be performed by user settings, or may be performed wirelessly.

Then, based on the detected flicker value, the flicker detection unit 106a holds the flicker waveform as a COS function with the period and coefficient as variables. In this embodiment, since the period is 10 ms, the flicker waveform is represented by a function of | COS2π · t / 10 × 10 ⁻³ |.

  When flicker is detected in step S2, the image processing IC 106 switches to aperture-priority exposure control since the flicker varies depending on the shutter speed, and calculates the relationship between the detected flicker waveform and the exposure timing of the CMOS sensor 101. (Step S3).

  FIG. 3 shows the relationship between the detected flicker waveform and the exposure timing of the CMOS sensor. The flicker waveform 300 is restored based on the discrete flicker information detected in S1 and has a period of 100 Hz. Reference numeral 301 represents the exposure start timing and exposure time of each line.

  The CMOS sensor 101 of this embodiment is a column readout type CMOS sensor having FD amplifiers for one line in the horizontal direction (one for each column). By changing the exposure start timing for each line, the exposure time T (electronic shutter speed) of each line is made uniform. In the figure, N is a variable representing a field. The timing at which an arbitrary field is exposed is N = 0, and the next field is N = 1, N = 2,. In this embodiment, the number of lines in each field is 1080 lines.

  Under a light source having a flicker phenomenon such as a fluorescent lamp, as shown in FIG. 3, the exposure amount of the sensor changes depending on the exposure timing of each line, so that images having different luminance levels in the vertical direction are generated.

  In step S3, the image processing IC 106 detects the time (phase: α [s]) from the point where the flicker waveform becomes zero (zero point) to the exposure start timing of the first line of an arbitrary field. The field (N) is set to 0 field. Hereinafter, α is a phase difference.

  FIG. 4 is a diagram showing the relationship between the exposure period of the first line and the exposure period of the second line in the 0 field and the flicker waveform representing the flicker of the flicker. The amount of light 401 actually exposed during the exposure period 400 of the first line is indicated by hatching. The time Dt [s] until the exposure of the second line is started with the start of exposure of the first line as a reference is usually 1 HD (time for reading image data for one line). The time Dt is common to the n-th line and the n + 1-th line, and is a time that does not depend on the shutter time or the like.

  The time α + T is the time when the exposure of the first line ends when the flicker brightness is zero (or the minimum value) as a reference. Here, T is the exposure time described above. The exposure period 404 for the second line is a period in which the time α + Dt is the exposure start point for the second line and the time α + Dt + T is the exposure end point for the second line.

Therefore, the exposure amount of the first line is a value obtained by integrating the function (| COS2π · t / 10 × 10 ⁻³ |) detected in S2 and held in the image processing IC 106 from time α to time α + T. . Similarly, the exposure amount of the second line is a value integrated from time α + Dt to time α + Dt + T. The exposure amount of the nth line is a value obtained by integrating from time α + (n−1) · Dt to time α + (n−1) · Dt + T. In this way, the exposure amounts L _{1 to} L ₁₀₈₀ for each line in the 0th field are calculated.

  As shown in FIG. 3, since the flicker cycle is 10 ms and the field cycle is 16.66 ms (1/60 ms), when the flicker cycle is repeated 5 times and the field reading is repeated 3 times, the phase becomes the phase difference α. Also, the integration range of the exposure amount in the first field is an integration range shifted by 1/60 [s] with respect to the integration range of each line in the 0 field. Similarly, the integration range of the exposure amount in the second field is an integration range shifted by 1/60 [s].

  Further, the exposure amounts of 3i field (i is a natural number), 3i + 1 field, and 3i + 2 field are the same as the exposure amounts of 0 field (N = 0), 1 field (N = 1), and 2 fields (N = 2), respectively. Become. Therefore, the correction data is divided into three types of correction data according to the field.

  In this embodiment, the 3i field is called 0 field, the 3i + 1 field is called 1 field, and the 3i + 2 field is called 2 field. In the image processing IC 106, the field number to be corrected is stored in the variable N. That is, when N = 0, it is 0 field, when N = 1, it is 1 field, and when N = 2, it is indicated that it is 2 fields. First, since 0 field is corrected, N = 0 is stored as an initial value.

In this way, the image processing IC 106 calculates and holds the exposure amount for 0 to 2 fields (step S4). The image processing IC 106 calculates correction amounts H _{1 to} H ₁₀₈₀ for each line corresponding to each field from the exposure amount obtained in S4 (step S5).

First, the image processing IC 106 selects the largest (brighter) numerical value among the exposure amounts L _{1 to} L ₁₀₈₀ among the fields, and sets the largest value as the reference value. When the exposure amount serving as the reference value is L _ref , the exposure amount of the line for calculating the correction amount is L _n , and the correction amount is H _n , the correction amount H _n is calculated by Equation (1). Here, n represents a line number.

H _n = −20 log L _n / L _ref [dB] (1)
In this way, the correction amount for each line of N = 0 to 2 is calculated, and the correction amount of each field is set as correction amount 0, correction amount 1, and correction amount 2, respectively.

  The image processing IC 106 corrects the actually captured image data using, for example, 0-field correction data, and outputs an image (step S6). Specifically, in this correction / output processing, the image data before correction is set to Dn, the coefficient for maintaining an appropriate exposure level is set to R (where 0 <R <1), and the corrected image data Dn ′ Then, the corrected image data Dn ′ is calculated according to Equation (2).

Dn ′ = R * Dn * Hn (2)
The image processing IC 106 takes in the image data of the next field from the CMOS sensor 101 (step S7), and detects the presence or absence of flicker by the flicker detection unit 106a (step S8). When the absence of flicker is detected, the image processing IC 106 returns to the process of step S1, returns to the normal imaging operation through S1 and S2, and outputs the image data of the next field (step S11). Thereafter, the image processing IC 106 returns to the process of step S1.

  On the other hand, if the presence of flicker is detected in step S2, the image processing IC 106 increases the field N to be corrected by 1 to N = N + 1, and changes the field to be corrected to the next field (step S9). At this time, when N = 3, the image processing IC 106 stores N = 0.

  Then, the image processing IC 106 determines whether or not the exposure time (electronic shutter speed) when capturing the image data of the previous field for which the correction amount is calculated is different from the exposure time when capturing the image data of the next field in S7. (Step S10). When the electronic shutter speed is varied and the exposure time is different, the image processing IC 106 returns to the process of step S4. That is, when the exposure time T at the time of creating the correction amount changes, the integration range at the time of calculating the exposure amount also changes, so the image processing IC 106 creates new correction data based on the new exposure time T in the processing after S4.

  On the other hand, when there is no change in the exposure time in S10, the image processing IC 106 determines which of the correction amount 0, the correction amount 1, and the correction amount 2 based on the value stored in the variable N in the field of the image data read in S7. Is selected, and the process returns to step S6 to correct the image data.

  As described above, when the flicker is detected, the imaging apparatus according to the first embodiment calculates and corrects the correction amount from the exposure start timing, the flicker fluctuation phase difference, and the number of read fields. Since correction is performed by calculating a correction amount to be multiplied for each line, correction can be performed so as to immediately follow fluctuations in flicker, and the influence of flicker can be reduced. Thus, correction data (correction amount) can be determined before image data is output, and flicker correction can be performed in a short time without impairing image quality.

  Further, since the correction amount is calculated using the ratio between the exposure amount of the predetermined line and the exposure amount of the line having the largest value, the correction amount can be easily calculated. Further, since the luminance level of a part of the subject area is output as the flicker level, the flicker level can be output in a short time with a small amount of data. Also, by counting the number of fields, the same correction data can be used for each predetermined number of fields, and the field image can be corrected easily.

[Second Embodiment]
Since the configuration of the imaging apparatus in the second embodiment is the same as that of the first embodiment, description thereof is omitted by using the same reference numerals. Here, operations different from those in the first embodiment will be described.

  FIG. 5 is a flowchart showing the procedure of flicker correction processing in the second embodiment. This process is executed by the image processing IC 106. As in the first embodiment, the subject light that has passed through the lens is converted into an electrical signal by the CMOS sensor 101, further output as digital image data by the AFE unit 103, and input to the image processing IC 106.

  As in the first embodiment, the image processing IC 106 measures flicker at a sampling frequency of 10 KHz (step S11). The image processing IC 106 detects the presence or absence of flicker based on the flicker signal input through the level conversion unit 105 (step S12).

  When the absence of flicker is detected, the image processing IC 106 outputs the image data by a normal imaging operation (step S20). Thereafter, the image processing IC 106 returns to the process of step S11. On the other hand, when the flicker phenomenon has occurred, the image processing IC 106 performs the processing after step S13.

  The image processing IC 106 changes to aperture-priority exposure control, and obtains the phase difference α between the read start position of the first line of the 0 field and the zero point of the flicker waveform as in the first embodiment (step S13). . Here, in the first embodiment, the correction amount is calculated, but in the second embodiment, correction data corresponding to the exposure time, phase difference, period, and field is stored in advance in the memory unit (see FIG. (Not shown) as a table.

FIG. 6 is a diagram showing a correction data table stored in the memory unit in the image processing IC 106. Figure 6 is a flicker cycle 100 Hz (utility frequency 50Hz band), the correction data when the phase difference alpha = alpha ₁ is shown.

In the figure, the exposure time T is represented by T1 to Tm (m is a natural number). The field number is represented by N = 0-2, and corresponds to 0-2 fields in the first embodiment. The line number n is represented by n = 1 to 1080, and n1 to n1080 represents the number of lines. In the drawing, the correction amount Hn represented by “H _N0n1 ” or the like indicates actual correction data. For example, when the phase difference α = α ₁ , flicker cycle 100 Hz, T = T 1 _{, and} N = 0, the correction data in the thick frame 600 is selected.

  The image processing IC 106 obtains an exposure time from the electronic shutter speed setting value in the exposure control, and selects a correction data table having an equivalent exposure time from the exposure times T1 to Tm in FIG. Furthermore, the image processing IC 106 selects a correction data table for each line by selecting, for example, a 0 field, which is a field to be corrected (step S14).

  The image processing IC 106 performs correction by amplifying the image data to be output by multiplying the correction value by the correction data for each line in the selected correction data table, and outputs the corrected image data (step S15). . In this correction / image output processing, as in the first embodiment, the image data before correction is Dn, the coefficient for maintaining the appropriate exposure level is R, the correction amount is Hn, and the image data Dn ′ after correction is used. The corrected image data Dn ′ is calculated according to the above-described equation (2).

  Thereafter, the image processing IC 106 takes in the image data of the next field (step S16). In parallel with the capture of the image data, the image processing IC 106 detects the presence or absence of flicker based on the output from the flicker sensor 104 (step S17).

  When the absence of flicker is detected, the image processing IC 106 returns to the process of step S11, returns to the normal imaging operation through S11 and S12, and outputs the image data of the next field (step S20). Thereafter, the image processing IC 106 returns to the process of step S11.

  On the other hand, if the presence of flicker is detected in S12, the image processing IC 106 increments the correction field by 1 to set N = N + 1, and sets the correction field to 1 field (step S18). The image processing IC 106 determines whether there is a change in the electronic shutter speed (step S19). When there is a change in the electronic shutter speed, the image processing IC 106 returns to the processing after step S14, selects correction data again using the exposure time T, and performs correction. On the other hand, if there is no change in the electronic shutter speed in S19, the image processing IC 106 returns to the processing in step S15 and corrects / outputs the image data of the next field.

  As described above, according to the imaging apparatus of the second embodiment, the flicker correction can be performed in a shorter time by using the correction amount stored in the table. Therefore, correction can be performed so as to immediately follow fluctuations in flicker, and the influence of flicker can be reduced.

  The present invention is not limited to the configuration of the above-described embodiment, and any configuration can be used as long as the functions shown in the claims or the functions of the configuration of the present embodiment can be achieved. Is also applicable.

It is a block diagram which shows the structure of the imaging device in 1st Embodiment. It is a flowchart which shows the procedure of a flicker correction process. It is a figure which shows the time change of a flicker signal when the flicker phenomenon has generate | occur | produced. It is a figure which shows the relationship between the exposure period of the 1st line of 0 field, the exposure period of the 2nd line, and the flicker waveform showing the flickering light and dark. 10 is a flowchart illustrating a procedure of flicker correction processing according to the second embodiment. 3 is a diagram showing a correction data table stored in a memory unit in the image processing IC 106. FIG.

Explanation of symbols

101 CMOS sensor 103 AFE unit 104 Flicker sensor 106 Image processing IC
106a Flicker detection unit 106b Phase / period detection unit 106c Correction unit

Claims (6)

An image sensor in which a plurality of light receiving units are arranged for each line and for each column;
Electronic shutter means for controlling the exposure start timing of the image sensor for each line to vary the exposure time;
Flicker detection means for detecting flicker in which the brightness of the light source fluctuates according to a predetermined frequency and outputting the detected flicker level;
Period detecting means for detecting a flicker period of the detected flicker;
A phase difference calculating means for calculating a phase difference from a time when the flicker level is minimum to an exposure start timing of a predetermined line of the image sensor when the flicker is detected;
Correction means for correcting image data from the image sensor for each line based on the calculated phase difference, the detected flicker period, and the variable exposure time;
An image pickup apparatus that outputs the image data corrected for each line as a field image.   The correction means calculates the correction amount using the ratio of the exposure amount of a predetermined line and the reference value, using the exposure amount of the line that is the largest of the exposure amounts of each line as a reference value, and calculating the calculation amount The imaging apparatus according to claim 1, wherein the image data of the predetermined line is corrected based on the corrected amount.   The imaging apparatus according to claim 1, wherein the flicker detection unit outputs a luminance level of a part of a subject area imaged by the imaging element as the flicker level. The field image when calculating the phase difference is set to 0 field, and includes a counting unit that counts the number of fields.
The imaging apparatus according to claim 1, wherein the correction unit performs correction based on the counted field number in addition to the phase difference, the flicker cycle, and the exposure time.   The correction unit stores the calculated correction amount in a table in advance, and uses the correction amount stored in the table when correcting the image data output from the image sensor for each line. The imaging apparatus according to claim 2. A flicker correction method for an imaging apparatus having an imaging element in which a plurality of light receiving units are arranged for each line and for each column,
An electronic shutter means for controlling the exposure start timing of the image sensor for each line and varying the exposure time;
Flicker detecting means for detecting flicker in which the brightness of the light source varies according to a predetermined frequency, and outputting the detected flicker level;
A period detecting means for detecting a flicker period of the detected flicker;
When the flicker is detected, calculating a phase difference from a time when the flicker level is minimum to an exposure start timing of a predetermined line of the image sensor;
Correcting image data from the image sensor for each line based on the calculated phase difference, the detected flicker period and the variable exposure time;
And a step of outputting the image data corrected for each line as a field image.

Images