JP2015192345A - Flicker reduction device, program therefor, and flicker reduction system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of estimating a flicker component included in a captured image with high accuracy and surely removing the estimated flicker component from the captured image by means of signal processing.SOLUTION: A flicker reduction device 1 is configured to generate a flicker reduced image from which a flicker component included in a captured image is removed, the captured image being captured by an imaging apparatus Cam with a frame frequency fhigher than a lighting frequency f. The flicker reduction device 1 includes: flicker component estimation means 11 for estimating the flicker component included in the captured image; and flicker component removal means 12 for generating the flicker reduced image for which the flicker component is removed from the captured image, by calculating a differential between the flicker component estimated by the flicker component estimation means 11 and the captured image.

Description

  The present invention relates to a technique for reducing a flicker component contained in a captured image captured by an imaging device having a frame frequency (vertical synchronization frequency) larger than an illumination frequency.

  Currently, high-resolution moving images such as Super Hi-Vision are being picked up. On the other hand, in order to improve not only the resolution but also the image quality, an imaging apparatus capable of imaging at a frame frequency higher than that of high vision (frame frequency: 60 Hz) has been studied and prototyped. In the ITU-R standard (Rec. ITU-R BT. 2020), 120 Hz is defined as the frame frequency of Super Hi-Vision.

  As a problem in capturing a moving image at such a high frame frequency, there is a flicker (image level temporal variation) problem. Flicker occurs when a moving image is captured by an imaging device having a frame frequency greater than the illumination frequency under illumination with a large luminance change (light amount change) such as a halogen lamp, a mercury lamp, or a fluorescent lamp. Here, the illumination frequency is twice the power frequency of the illumination. For example, in Japan, the power frequency of lighting in East Japan is 50 Hz. In this case, if the frame frequency of the imaging device is 120 Hz defined in the above-described standard, the frame frequency of the imaging device is 20 Hz higher than the illumination frequency due to {frame frequency of the imaging device− (power supply frequency of illumination × 2)}. Since it becomes large, flicker occurs in the captured image.

  Note that illumination that causes flicker in captured images is rarely used in broadcast station studios. However, in large sports stadiums, mercury lamps are still used as the main light source. Therefore, flickering is inevitable when shooting sports broadcasts at a high frame frequency, such as a super high-definition camera.

  Since such flicker is a major factor that degrades the image quality of a captured image, various methods for suppressing flicker have been tried. As an example, there has been proposed a technique for preventing flicker by inserting a shutter shorter than one frame time at the time of imaging and matching the frame frequency and the illumination frequency (see Patent Documents 1 and 2).

JP 2007-96556 A JP 2003-189173 A

  In the above-described method, for example, when shooting with a high-definition camera with an illumination power supply frequency of 50 Hz and a frame frequency of 60 Hz, the occurrence of flicker is prevented by inserting a 1/100 second shutter at the time of imaging. Is possible. However, for example, when imaging is performed with a Super Hi-Vision camera having a frame frequency of 120 Hz in an area where the power supply frequency of illumination is 50 Hz, it is impossible in principle to insert a shutter longer than one frame time. / The shutter of 100 seconds cannot be inserted. Therefore, in this case, as described above, it is inevitable that flicker occurs in the captured image due to a difference between the frame frequency and the illumination frequency of the imaging device.

  Therefore, the present invention provides a flicker reduction apparatus and program capable of accurately estimating flicker components included in a captured image and reliably removing the estimated flicker components from the captured image by signal processing, and flicker reduction. The problem is to provide a system.

  In order to solve the above-described problem, the present invention provides a flicker reduction device for reducing a flicker component included in a captured image captured by an imaging device having a frame frequency greater than an illumination frequency. Removing means.

According to such a configuration, the flicker reducing device uses the flicker component estimating means to set the captured image of the frame number n (1 ≦ n ≦ N) to I (n), the flicker component frequency to f _f , and the frame frequency to f and _Cam, when the lighting frequency is f _L, is estimated flicker component f (n) of the following expression.

Then, the flicker reducing apparatus removes the flicker component from the captured image by calculating the difference between the flicker component estimated by the flicker component estimating unit and the captured image by the flicker component removing unit.
As a result, the flicker reduction device can acquire a captured image with reduced flicker components.

  Here, the flicker reduction apparatus of the present invention is realized by a flicker reduction program for causing hardware resources such as a CPU (Central Processing Unit), a memory, and a hard disk of a computer to cooperate as flicker component estimation means and flicker component removal means. You can also This program may be distributed through a communication line, or may be distributed by writing in a recording medium such as a CD-ROM or a flash memory.

  The present invention also provides a flicker reduction system for reducing a flicker component included in a captured image captured by an imaging device having a frame frequency greater than the illumination frequency, the light receiving element, the illumination frequency estimation device, and the flicker reduction device. It is characterized by providing.

According to such a configuration, the flicker reduction system measures the intensity of the illumination light along the time series by the light receiving element, and outputs a waveform indicating a change in the intensity of the illumination light within the measurement time.
Further, the flicker reduction system receives an output waveform from the light receiving element by the illumination frequency estimation device, and estimates the illumination frequency based on the output waveform.

Further, the flicker reduction system compares and determines whether or not the illumination frequency estimated by the illumination frequency estimation device is smaller than the known frame frequency of the imaging device by the frequency comparison and determination unit of the flicker reduction device. When the flicker component estimating unit of the flicker reducing device determines that the illumination frequency is lower than the frame frequency by the flicker reducing unit, the flicker reducing system obtains a captured image of frame number n (1 ≦ n ≦ N). When I (n) is set, the flicker component frequency is f _f , the frame frequency is f _Cam , and the illumination frequency is f _L , the flicker component f (n) is estimated by the following equation.

The flicker reduction system obtains a flicker-reduced image obtained by removing the flicker component from the captured image by taking the difference between the flicker component estimated by the flicker component estimating unit and the captured image by the flicker component removing unit of the flicker reducing device. Generate.
Thus, the flicker reduction system can acquire a captured image with reduced flicker components.

The present invention has the following excellent effects.
According to the present invention, it is possible to obtain a captured image with a reduced flicker component by estimating flicker components included in the captured image with high accuracy and removing the estimated flicker components from the captured image by signal processing. Therefore, according to the present invention, it is possible to suppress deterioration in image quality of a captured image due to a flicker component.

It is a block diagram which shows the structure of the flicker reduction apparatus which concerns on embodiment of this invention. It is a graph which shows the output example of the captured image imaged by the imaging device. The graph which shows the output example of the picked-up image imaged with the imaging device, the flicker component estimated by the flicker reduction apparatus which concerns on embodiment of this invention, and the flicker reduction image produced | generated by the flicker reduction apparatus which concerns on embodiment of this invention is there. It is a flowchart which shows operation | movement of the flicker reduction apparatus which concerns on embodiment of this invention. It is a block diagram which shows the structure of the flicker reduction system which concerns on embodiment of this invention. It is a graph which shows the example of an output of the light receiving element shown in FIG. It is a flowchart which shows operation | movement of the flicker reduction system which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, the same name and reference sign indicate the same or the same member in principle, and the detailed description is omitted as appropriate.

[Configuration of flicker reduction device]
As shown in FIG. 1, the flicker reducing apparatus 1 according to the embodiment of the present invention is a flicker that is an image obtained by removing a flicker component from a captured image I (n) captured by an imaging apparatus Cam having a frame frequency higher than an illumination frequency. A reduced image is generated. Hereinafter, the frame frequency is expressed as “frame frequency f _Cam ”, and the illumination frequency is expressed as “illumination frequency f _L ”. Here, it is assumed that the frame frequency f _Cam and the illumination frequency f _L are known.

The flicker reduction apparatus 1 includes a flicker component estimation unit 11 and a flicker component removal unit 12.
The flicker component estimation means 11 estimates a flicker component included in a captured image captured by the imaging device Cam. In the following, for the sake of simplicity, a case where the captured image captured by the imaging device Cam is a monochrome image will be described as an example.
Here, the captured image including the flicker component is represented as I (x, y, n). The captured image I (x, y, n) is considered to be the sum of the captured image (flicker reduced image) J (x, y, n) and the flicker component f (x, y, n) that do not include the flicker component. Therefore, it is expressed by the following equation (3).

  Therefore, the flicker component estimation means 11 calculates the flicker component f (x, y, n) included in the captured image I (x, y, n) from the captured image I (x, y, n) shown in the equation (3). n) is estimated.

Of the captured image I (x, y, n), a time-change output at a position (x ₀ , y ₀ ) where a bright image level output (80%) is obtained is defined as I (n). For example, the flicker component estimation unit 11 designates the position (x ₀ , y ₀ ) in accordance with an instruction input via an input unit (not shown).

Here, FIG. 2 is a graph illustrating an output example of a captured image when a moving image is captured by the imaging device Cam under illumination with a large luminance change (light amount change). In the example illustrated in FIG. 2, it is assumed that the frame frequency f _Cam of the imaging device _Cam is 120 Hz. Note that the imaging device Cam is assumed to be a camera that can capture an image of a subject at a high frame frequency f _Cam such as high-definition or super high-definition.

  In the graph shown in FIG. 2, the horizontal axis represents time [s], the vertical axis represents the image level, and the waveform represents the captured image (image output) I (n). n is a frame number. Here, since a 16-gradation image is picked up by a conventional imaging device, the image level is represented by 0 to 65535. However, in the graph shown in FIG. 2, a portion where a bright image output is obtained (image level) Only 48000-52500).

As shown in FIG. 2, the captured image I (n) is represented by a sine wave whose image level fluctuates around 48700 and 51000 in a short time. That is, it can be seen that the image level (brightness, luminance) temporal variation occurs in the image output that should continue to have a constant value.
When the captured image I (n) illustrated in FIG. 2 is captured in an area where the power supply frequency of the illumination is 50 Hz, the illumination frequency f _L (the power supply frequency of the illumination × 2 = 100 Hz) and the frame frequency f of the imaging device _This means that a flicker component f (n), which is a component representing temporal variation of the image level (brightness, luminance) caused by the deviation from _Cam (120 Hz), is included.
The flicker component f (n) is a sine wave and is expressed by the following equation (4).

In the equation (4), f _f is the frequency of the flicker component f (n), and is represented by the frame frequency f _Cam of the imaging device Cam _−the illumination frequency f _L.
If the amplitude S and phase φ of the flicker component f (n) shown in the equation (4) can be estimated, the flicker component f (n) can be estimated. However, the calculation process for estimating the amplitude S and the phase φ of the flicker component f (n) is complicated and unrealistic because the processing load is large. Therefore, the flicker reduction apparatus 1 according to the present embodiment can reduce the processing load by estimating the flicker component f (n) with a mathematical expression that is relatively easy to perform arithmetic processing.

  Specifically, the flicker component estimation means 11 shown in FIG. 1 estimates the flicker component f (n) by the following equation (5).

  As shown in the equation (4), the amplitude S and the phase φ of the sine wave of the flicker component f (n) are expressed by a sin function and a cos function. As shown in 5), the amplitude S and the phase φ are divided into a sin function and a cos function and treated as a composite function thereof. As a result, the flicker component estimation means 11 can easily estimate the flicker component f (n) by obtaining the coefficients A and B shown in the equation (5).

  The relationship between the amplitude S and the phase φ in the equation (4) and the coefficients A and B in the equation (5) is expressed by the following equation (6).

  Here, the range in which the flicker component f (n) is estimated is (1 ≦ n ≦ N). N represents the number of frames used to estimate the flicker component f (n), and is set to a value in which an integral multiple of one cycle of the flicker component f (n) falls within the estimated range (1 ≦ n ≦ N). Is done.

Here, when the flicker component f (n) is actually estimated from the captured image (image output) I (n), it is necessary to subtract the influence of the DC component C superimposed on the flicker component f (n). . The direct current component C can be considered as an average value in a range (1 ≦ n ≦ N) in which the flicker component f (n) is estimated.
Therefore, the DC component C is obtained as in the following equation (7).

  Further, the flicker component estimating means 11 sets the function I ′ (n) = I (n) −C, and fits the function I ′ (n) to the function f (n) shown in the equation (5).

  The flicker component estimating means 11 uses the function I ′ (n) and the function I ′ (n) as shown in the following equation (8), using the coefficients A and B of the function f (n) shown in the equation (5). ) With a coefficient that minimizes a square error with the function f (n) to be fitted.

  When this condition is solved analytically, the coefficients A and B of the function f (n) shown in the equation (5) are obtained as the following equation (9).

  As described above, the flicker component estimating means 11 obtains the coefficients A and B of the function f (n) shown in the above equation (5). The flicker component estimation means 11 estimates the flicker component f (n) by substituting the obtained coefficients A and B into the equation (5). The flicker component f (n) estimated in this way is output to the flicker component removal means 12.

  The flicker component removal unit 12 receives the flicker component estimation result from the flicker component estimation unit 11, inputs the captured image from the imaging device Cam, and generates a flicker reduced image by subtracting the flicker component from the captured image. It is.

  Here, the captured image I (n) of the frame number n, the flicker component estimation unit 11, the flicker component f (n) included in the captured image I (n), and the flicker component removal unit 12 FIG. 3 shows a graph showing the relationship between the flicker reduced image e (n) = I (n) −f (n) generated by taking the difference between the flicker component f (n) and the captured image I (n). It was. In FIG. 3, the flicker component f (n), the captured image I (n), and the flicker reduced image e (n) are represented in the same graph for easy understanding. DC component C is added to.

  In the example shown in FIG. 3, N = 36. That is, the flicker component estimation means 11 estimates the flicker component f (n) using 36 frames (captured image for 0.3 sec. Imaging time) of the captured image I (n) captured at a frame frequency of 120 Hz. did. Then, the flicker component removing unit 12 captures the flicker component f (n) estimated by the flicker component estimating unit 11 using the captured image I (n) for the imaging time of 0.3 seconds for the imaging time of 1 second. The flicker-reduced image e (n) was generated by applying to the image I (n).

  As shown in FIG. 3, the output of the captured image I (n) is represented by a sine wave in which the image level moves back and forth in the vicinity of 48700 and 51000 in a short time, and time fluctuation occurs in the image level. Can be confirmed. On the other hand, as shown in FIG. 3, the flicker component removal unit 12 removes the flicker component f (n) estimated by the flicker component estimation unit 11 from the captured image I (n), and the flicker reduced image e (n ) Confirms that the image level is substantially constant, and that the image level does not substantially vary with time.

Here, as described above, the flicker component f (n) estimated by the flicker component estimation means 11 is the flicker component of the entire actual captured image I (x, y, n) captured by the imaging device Cam. This is obtained using frames for the time range (1 ≦ n ≦ N) of the position (x ₀ , y ₀ ) for estimating f (n).
That is, the flicker component f (n) estimated by the flicker component estimation means 11 includes the position (x ₀ ,) where the flicker component f (n) is estimated in the entire actual captured image I (x, y, n). Only the fluctuation of the image level within the time range (1 ≦ n ≦ N) of y ₀ ) is reflected.

  On the other hand, the actual captured image I (x, y, n) has an image level that changes every moment according to the pixel position (x, y). Therefore, the flicker component f (n) estimated by the flicker component estimation means 11 is applied to the entire captured image I (x, y, n) to obtain the flicker reduced image J (x, y, n). Needs to be multiplied by a correction coefficient I (x, y, n) / C corresponding to the image level of each pixel position (x, y) of the captured image I (x, y, n).

  Specifically, the flicker component removing unit 12 uses the following equation (10) to reduce the flicker reduced image J (x, y, n) obtained by removing the flicker component f (n) from the captured image I (x, y, n). )

Next, the operation of the flicker reduction apparatus 1 will be described with reference to FIG.
As shown in FIG. 4, the flicker reducing apparatus 1 uses the flicker component estimation unit 11 to calculate the flicker component f of the captured image I (n) captured by the imaging apparatus Cam using the equations (5) to (9). (N) is estimated (step S1). The flicker reducing apparatus 1 outputs the flicker component f (n) estimated by the flicker component estimating unit 11 to the flicker component removing unit 12.

  Then, the flicker reduction device 1 receives the estimation result of the flicker component f (n) from the flicker component estimation unit 11 by the flicker component removal unit 12, and is imaged by the imaging device Cam using the equation (10). A flicker-reduced image J (x, y, n) is generated from the captured image I (x, y, n) (step S2). The flicker reducing apparatus 1 outputs the generated flicker reduced image J (x, y, n) to the outside by the flicker component removing unit 12.

The flicker reduction apparatus 1 operates as described above.
According to the flicker reduction apparatus 1 according to the embodiment of the present invention described above, the flicker component estimation unit 11 can easily and accurately estimate the flicker component included in the captured image.
Further, according to the flicker reducing apparatus 1, the flicker component removing unit 12 removes the estimated flicker component from the captured image by taking the difference between the flicker component estimated by the flicker component estimating unit 11 and the captured image. A flicker-reduced image can be generated.
As described above, according to the flicker reducing apparatus 1, since the flicker component included in the captured image can be reduced by the signal processing, it is possible to suppress deterioration in the image quality of the captured image due to the flicker component.

[Flicker reduction system configuration]
Next, the flicker reduction system 100 according to the embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 5, the flicker reduction system 100 generates a flicker-reduced image in which a flicker component included in the captured image is reduced from a captured image captured by the imaging device Cam having a frame frequency higher than the illumination frequency. The flicker reduction device 1A, the light receiving element 2, and the illumination frequency estimation device 3 are provided. Hereinafter, the frame frequency is expressed as “frame frequency f _Cam ”, and the illumination frequency is expressed as “illumination frequency f _L ”. Here, it is assumed that the frame frequency f _Cam is known and the illumination frequency f _L is unknown.

Here, the imaging device Cam captures a moving image of a subject, and here refers to a camera that can capture the subject at a high frame frequency f _Cam such as high-definition or super high-definition.
For example, when a moving image of a subject is captured by the imaging device Cam having a frame frequency f _Cam of 120 Hz under the illumination L having a large luminance change (light amount change), a captured image (image output) I as shown in FIG. (N) is obtained. When the captured image I (n) illustrated in FIG. 2 is captured in an area where the power supply frequency of the illumination is 50 Hz, the illumination frequency f _L (the power supply frequency of the illumination × 2 = 100 Hz) and the frame frequency of the imaging device Cam This means that the flicker component f (n), which is a component representing the temporal variation of the image level (brightness, luminance) caused by the deviation from f _Cam (120 Hz), is included.

Again, as shown in FIG. 5, the flicker reduction apparatus 1 </ b> A includes a flicker component estimation unit 11, a flicker component removal unit 12, and a frequency comparison determination unit 13.
When the flicker component estimation unit 11 receives a notification that the illumination frequency f _L is smaller than the frame frequency f _Cam of the imaging device Cam from the frequency comparison determination unit 13 described later, the flicker component estimation unit 11 is included in the captured image captured by the imaging device Cam. The flicker component is estimated.

The flicker component removal unit 12 receives the flicker component estimation result from the flicker component estimation unit 11, inputs the captured image from the imaging device Cam, and generates a flicker reduced image by subtracting the flicker component from the captured image. It is.
The flicker component estimating means 11 and the flicker component removing means 12 are as described above with reference to FIG.

The frequency comparison / determination means 13 compares the illumination frequency f _L estimated by the illumination frequency estimation device 3 to be described later with the known frame frequency f _Cam of the imaging device Cam, and the illumination frequency f _L is the frame frequency of the imaging device Cam. It is determined whether it is smaller than f _Cam . Frequency comparison determination unit 13, the lighting frequency _{f L} and an imaging device frame frequency _{f Cam} and results of comparison of the Cam, when the lighting frequency _{f L} is the frame frequency _{f Cam} smaller than the imaging device Cam, the flicker component estimating unit 11 Notify that.

  The light receiving element 2 is a sensor that is disposed in the vicinity of the imaging device Cam, measures the intensity of illumination light incident from the illumination L installed in the imaging environment, and outputs the measured illumination light intensity by changing it to an electrical signal. is there. Here, the light receiving element 2 generates a voltage according to the intensity of the illumination light incident from the illumination L, and outputs a waveform indicating the change of the output voltage in the measurement time along the time series. As such a light receiving element 2, for example, a general photodiode can be used.

  Here, FIG. 6 is a graph showing an output example of the light receiving element 2 when the illumination L is a halogen lamp. In the graph shown in FIG. 6, the horizontal axis represents time [s], and the vertical axis represents output voltage [v]. The output waveform from the light receiving element 2 is output to the illumination frequency estimation device 3.

Lighting frequency estimating apparatus 3, the output waveform shown in chronological changes in the output voltage at the measurement time input from the light receiving element 2, and estimates the illumination frequency f _L of the imaging environment from the output waveform.
Here, the illumination frequency estimation device 3 detects the time between the peaks of the output waveform input from the light receiving element 2 (the time until the next peak comes from the peak), and the illumination frequency based on the detected time between the peaks. to estimate the f _L. For example, the lighting frequency estimating apparatus 3 estimates the reciprocal of the time between the detected peak and the illumination frequency f _L. In the case of the output waveform shown in FIG. 6, since the time between the peak p ₁ and the peak p ₂ is 0.01 [s], the illumination frequency estimation device 3 estimates the illumination frequency f _L as 100 Hz. Lighting frequency estimating apparatus 3 outputs a lighting frequency f _L estimated flicker reduction apparatus 1A.

[Operation of flicker reduction system]
Next, the operation of the flicker reduction system 100 according to the embodiment of the present invention will be described with reference to FIG. In the following, for the sake of simplicity, a case where the captured image captured by the imaging device Cam is a monochrome image will be described as an example.
As shown in FIG. 7, the flicker reduction system 100 measures the light intensity of the illumination L by the light receiving element 2 (step S11). The flicker reduction system 100 outputs, by the light receiving element 2, a waveform that represents a change in the intensity of illumination light within a measurement time along a time series.

Further, the flicker reduction system 100 receives the waveform output from the light receiving element 2 by the illumination frequency estimation device 3, detects the time between peaks of the output waveform, and based on the detected time between peaks, the illumination frequency estimating the f _L (step S12). Flicker reduction system 100, by the illumination frequency estimator 3, and outputs the lighting frequency f _L estimated flicker reduction apparatus 1A.

Furthermore, the flicker reduction system 100 compares the illumination frequency f _L output from the illumination frequency estimation device 3 with the known frame frequency f _Cam of the imaging device Cam by the frequency comparison determination unit 13 of the flicker reduction device 1A. lighting frequency _{f L} is equal to or frame frequency _{f Cam} less than or of the imaging device Cam (step S13).

Frequency comparison determination unit 13, the lighting frequency _{f L} and an imaging device frame frequency _{f Cam} and results of comparison of the Cam, Yes if (step S13 where the illumination frequency _{f L} is determined as the frame frequency _{f Cam} smaller than the imaging device Cam ), The flicker component estimation means 11 is notified of this.

Meanwhile, flicker reduction system 100, by the frequency comparison determination unit 13 of the flicker reduction apparatus 1A, the lighting frequency _{f L} and an imaging device Cam frame frequency _{f Cam} and results of comparison of the frame frequency of the lighting frequency _{f L} is an imaging device Cam If it is determined that it is greater than f _Cam (No in step S13), the process is terminated.

Then, the flicker reduction system 100, the flicker component estimating unit 11 of the flicker reduction apparatus 1A, enter the captured image from the imaging device Cam, further from the frequency comparison determination unit 13, the lighting frequency f _L of the imaging device Cam frame When a notification that the frequency is smaller than the frequency f _Cam is input, the flicker component f (n) of the captured image I (n) captured by the imaging device Cam is estimated using the equations (5) to (9) (steps). S14). The flicker reducing apparatus 1 </ b> A outputs the estimated flicker component f (n) to the flicker component removing unit 12 by the flicker component estimating unit 11.

Then, the flicker reducing device 1A inputs the estimation result of the flicker component f (n) from the flicker component estimating unit 11 by the flicker component removing unit 12, and also inputs the captured image from the imaging device Cam, and the equation (10) Is used to generate the flicker-reduced image J (x, y, n) from the captured image I (x, y, n) captured by the imaging device Cam (step S15).
The flicker reduction system 100 operates as described above.

According to the flicker reduction system 100 described above, when the lighting frequency f _L of the imaging environment is unknown, by the light receiving element 2, by measuring the time variation of the intensity of the illumination light of the illumination L of the imaging environment, lighting frequency estimation the device 3, it is possible to estimate the illumination frequency f _L of the imaging environment based on the measurement result by the light receiving element 2.

Then, according to the flicker reduction system 100, when the lighting frequency f _L of the imaging environment is unknown, the flicker reduction apparatus 1A, whether lighting frequency f _L is smaller than the frame frequency f _Cam imaging device Cam Based on the result of the comparison determination, the operator can determine whether or not flicker reduction processing by the flicker reduction apparatus 1A is necessary.

Specifically, according to the flicker reduction system 100, the flicker reduction apparatus 1A, when the determination result that the illumination frequency f _L is larger than the frame frequency f _Cam is obtained, according to the imaging apparatus Cam as in the conventional method By inserting a shutter at the time of imaging, it is possible to acquire a captured image that does not cause flicker. Therefore, the operator can determine that the flicker reduction process by the flicker reduction apparatus 1A is unnecessary. Further, in that case, it is not necessary to perform the flicker reduction process by the flicker reduction apparatus 1A on the captured image captured by the imaging apparatus Cam, so that the processing load by the flicker reduction apparatus 1A can be reduced.

  In addition, this invention is not limited to above-described embodiment, A various deformation | transformation can be added in the range which does not deviate from the meaning.

  The flicker reduction apparatus 1 according to the above-described embodiment is based on a flicker reduction program for causing hardware resources such as a CPU (Central Processing Unit), a memory, and a hard disk of a computer to operate cooperatively as flicker component estimation means and flicker component removal means. It can also be realized. This program may be distributed through a communication line, or may be distributed by writing in a recording medium such as a CD-ROM or a flash memory.

  In addition, the present invention may be configured as an imaging device including the flicker reduction device 1 described above. According to such an imaging apparatus, it is possible to generate a flicker-reduced image in which the flicker component is reduced with high accuracy from the captured image. Therefore, it is possible to suppress deterioration in image quality of the captured image due to the flicker component.

  The flicker reduction apparatus 1A of the flicker reduction system 100 according to the above-described embodiment includes hardware resources such as a CPU (Central Processing Unit), memory, and hard disk of a computer, frequency comparison determination means, flicker component estimation means, flicker component removal means. It can also be realized by a flicker reduction program for cooperative operation. This program may be distributed through a communication line, or may be distributed by writing in a recording medium such as a CD-ROM or a flash memory.

In the flicker reduction system 100 according to the above-described embodiment, the illumination frequency estimation device 3 estimates the illumination frequency f _L based on the time between peaks of the output waveform output from the light receiving element 2. It is not limited to this. For example, the flicker reduction system 100 may estimate the illumination frequency f _L by Fourier transforming the output waveform output from the light receiving element 2 by the illumination frequency estimation device 3.

Further, the flicker reduction system 100 according to the aforementioned embodiment, by illuminating the frequency estimator 3, it is assumed that estimates the illumination frequency f _L based on the output waveform output from the light receiving element 2 is not limited to this .
Specifically, the flicker reduction system 100 may estimate a value twice the known power supply frequency in the imaging environment as the illumination frequency f _L by the illumination frequency estimation device 3. For example, if the imaging environment at East, since power supply frequency is 50 Hz, the lighting frequency estimating apparatus 3 estimates the illumination frequency _{f L} and 100 Hz. Further, for example, if the imaging environment in western Japan, the power supply frequency is in the 60 Hz, the lighting frequency estimating apparatus 3 estimates the illumination frequency _{f L} and 120 Hz.

According to this, it is possible to reduce the load of the process of estimating the lighting frequency f _L by the illumination frequency estimating apparatus 3. Furthermore, since the light receiving element 2 can be omitted, the configuration of the flicker reduction system 100 can be further simplified.

Further, the flicker reduction system 100 according to the aforementioned embodiment, the frequency comparison determination unit 13 of the flicker reduction apparatus 1A, when the lighting frequency f _L is determined to less than the frame frequency f _L, that to the flicker component estimating unit 11 However, this notification need not be performed.
In that case, the flicker reduction system 100 may automatically perform the flicker reduction process by the flicker component estimation means 11 and the flicker component removal means 12 of the flicker reduction apparatus 1A.

  Furthermore, in each of the above-described embodiments, the case where the captured image captured by the imaging device Cam is a monochrome image has been described as an example. Similarly, even if it is a color image, flicker reduction processing by the flicker reduction devices 1 and 1A. Is possible.

  When the captured image captured by the imaging device Cam is a color image (RGB), for example, the flicker reduction devices 1 and 1A perform flicker component estimation processing on the G image output by the flicker component estimation unit 11. Then, the flicker reducing devices 1 and 1A may generate the flicker reduced image by applying the flicker component estimation result for the G image output to the R / G / B image output by the flicker component removing unit 12.

  Further, for example, in the flicker reduction devices 1 and 1A, the flicker component estimation unit 11 estimates flicker components individually for the R / G / B image output, and the flicker component removal unit 12 performs R / G / B The flicker reduced image may be generated by applying the estimation result of each flicker component to the image output.

Furthermore, the flicker reduction processing by the flicker reduction devices 1 and 1A may be applied to a captured image that is captured by the imaging device Cam and stored in a storage unit (not shown).
In addition, the flicker component estimation process may be performed by the flicker component estimation unit 11 of the flicker reduction apparatuses 1 and 1A on the captured image captured in advance by the imaging device Cam. Then, the flicker reduction devices 1 and 1A may apply the flicker component estimation result obtained by the flicker component estimation unit 11 uniformly to the real-time image output by the flicker component removal unit 12 to generate a flicker reduced image.

  According to this, since the flicker component included in the real-time captured image can be reduced with high accuracy, it is possible to suppress deterioration in the image quality of the captured image broadcasted by relaying or the like. In addition, by estimating in advance what kind of flicker component appears in the captured image captured by the imaging device Cam in the imaging environment, for example, by estimating the flicker component before relaying, flicker during relaying Since there is no need to estimate the components, convenience is enhanced.

  In addition, the flicker reduction system 100 may further include an adjustment device that can adjust the values of the amplitude S and the phase φ of the flicker component f (n) estimated by the flicker component estimation means 11 of the flicker reduction device 1A. According to this, the flicker reduction system 100 can manually adjust the amplitude S and the phase φ of the flicker component f (n) estimated by the flicker component estimation means 11 using an adjustment device by an operator or the like. As a result, the flicker component contained in the captured image can be more reliably removed. As a result, the flicker component included in the captured image can be reduced with higher accuracy, so that deterioration of the image quality of the captured image due to the flicker component can be more reliably suppressed.

  The present invention may be configured as a flicker reduction system including the flicker reduction apparatus 1 and the adjustment apparatus described above, or configured as a flicker reduction system including the imaging apparatus including the flicker reduction apparatus 1 and the adjustment apparatus described above. May be.

DESCRIPTION OF SYMBOLS 1,1A Flicker reduction apparatus 11 Flicker component estimation means 12 Flicker component removal means 13 Frequency comparison determination means 2 Light receiving element 3 Illumination frequency estimation apparatus 100 Flicker reduction system Cam Imaging device

Claims (3)

A flicker reduction device for reducing a flicker component included in a captured image captured by an imaging device having a frame frequency greater than an illumination frequency,
When the captured image of the frame number n (1 ≦ n ≦ N) is I (n), the flicker component frequency is f _f , the frame frequency is f _Cam , and the illumination frequency is f _L , The flicker component f (n)

Flicker component estimation means for estimating by
A flicker reduction device comprising flicker component removal means for generating a flicker reduced image obtained by removing the flicker component from the captured image by taking the difference between the flicker component estimated by the flicker component estimation means and the captured image .   A flicker reduction program for causing a computer to function as the flicker reduction apparatus according to claim 1. A flicker reduction system for reducing a flicker component included in a captured image captured by an imaging device having a frame frequency greater than an illumination frequency,
A light receiving element that measures the intensity of the illumination light along a time series and outputs a waveform indicating a change in the intensity of the illumination light within a measurement time;
Input an output waveform from the light receiving element, and based on this output waveform, an illumination frequency estimation device that estimates the illumination frequency;
Frequency comparison determination means for comparing whether or not the illumination frequency estimated by the illumination frequency estimation apparatus is smaller than the known frame frequency of the imaging apparatus, and the illumination frequency is determined by the frequency comparison determination means. If it is determined that it is lower than the frame frequency,
When the captured image of the frame number n (1 ≦ n ≦ N) is I (n), the flicker component frequency is f _f , the frame frequency is f _Cam , and the illumination frequency is f _L , The flicker component f (n)

Flicker component estimation means for estimating the flicker component, and the flicker component generated by removing the flicker component from the captured image by taking the difference between the flicker component estimated by the flicker component estimation means and the captured image. A flicker reduction system comprising: a flicker reduction device including a component removing unit.

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