JP2005123776A - Flicker level / noise level detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flicker level / noise level detector adopting an inexpensive, versatile and downsized configuration. <P>SOLUTION: The flicker level / noise level detector is configured with: a luminance photometry logic 13 for calculating a luminance evaluation value by each frame; a segmentation means 7 for extracting only a video signal of an OB region; a selection means 8 for selecting a signal from the luminance photometry logic 13 or a signal from the segmentation means 7 and outputting the selected signal; and a level detector 9 for transmitting a flicker level detection output when the level detector 9 receives the signal from the luminance photometry logic 13 or a noise level detection output when the level detector 9 receives the signal from the segmentation means 7. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a flicker level / noise level detector used in video equipment such as an electronic camera, and more particularly to a flicker level / noise level detector having a general-purpose, downsized and inexpensive structure.

FIG. 8 is a block diagram showing a configuration of a conventional electronic camera.
The electronic camera in FIG. 8 includes a lens 1, an image sensor 2, an OB clamp circuit 3, a PGA (Programmable Gain Amp) 4, an ADC (Analog Digital Converter) 5, an LPF (Low Pass Filter) 12, and error detection. It comprises a detector (Error Detect) 11, a DAC (Digital Analog Converter) 10, luminance metering logic 13, and luminance control logic 14.

  Output signals from the lens 1 and the image sensor 2 are added by the OB clamp circuit 3 to a correction value input from the DAC 10 constituting the clamp control system (black level correction system). Then, the PGA 4 amplifies the output signal of the OB clamp circuit 3 based on the set predetermined gain (Gain), and the amplified signal is converted into a digital signal by the ADC 5. This digitized signal becomes an output signal and is fed back for correcting the black level in the clamp control system.

  The fed back digital signal is supplied to the LPF 12, and when the digital signal corresponding to the sensor output in the light shielding area is input, the LPF 12 averages the digital signal. Then, the error detector 11 detects the difference between the digital signal supplied from the LPF 12 and the target value of the black level (hereinafter referred to as “OB target value”), and a correction value according to the detected difference. Is output. The correction value is supplied to the DAC 10, and the DAC 10 converts the correction value into an analog form and outputs it to the OB clamp circuit 3.

  On the other hand, an output signal from the OB clamp circuit 3 is amplified with a predetermined gain by the PGA 4 and then supplied to an ADC (Analog to Digital Converter) 5. At this time, in order to effectively use the dynamic range of the ADC 5, the output signal from the OB clamp circuit 3 is amplified in the PGA 4 so that the input level to the ADC 5 does not exceed the dynamic range and becomes a higher input level. The The electronic shutter speed of the image sensor 2 and the gain (Gain) of the PGA 4 are set by the luminance control logic 14 described later.

Next, the output signal of PGA 4 is converted into a digital signal by ADC 5. Next, the luminance photometry logic 13 integrates the luminance of each pixel for one screen of the output signal of the ADC 5, and the integration result is used as a luminance evaluation value. The logic for generating the luminance evaluation value in the luminance photometry logic 13 is called luminance photometry logic.
As luminance metering logic, in addition to a method of simply integrating the luminance of pixels included in one screen, assuming that a subject is present near the center of the screen, a method of weighting and integrating pixels near the center, A method is used in which the screen is divided into a predetermined pattern, weighted, and integrated.

Next, the luminance control value is processed by the luminance control logic 14. In other words, a luminance target value that is a target value of the luminance level of the image is set in the luminance control logic 14 by a microcomputer or the like. Then, the luminance control logic 14 compares the luminance target value with the luminance evaluation value and calculates the error.
The brightness control logic 14 controls the electronic shutter speed based on the error. Specifically, when the brightness evaluation value is smaller than the brightness target value, the brightness control logic 14 determines that the image is dark and slows down the electronic shutter speed (lengthens the exposure time). Conversely, if the luminance evaluation value is greater than the luminance target value, the luminance control logic 14 determines that the image is bright and increases the electronic shutter speed (decreases the exposure time). As a result of such control, the luminance evaluation value can be brought close to the luminance target value.

Further, if the luminance evaluation value does not reach the luminance target value even when the electronic shutter speed is the slowest, the luminance control logic 14 performs control to adjust the gain of the PGA 4 and bring the luminance evaluation value closer to the luminance target value.
Here, when the electronic shutter speed is controlled by the luminance control logic 14, it is set to an integral multiple of the period of the horizontal synchronization signal of the image sensor 2 from the relationship with the structure of the image sensor 2. For example, if the period of the horizontal synchronizing signal is Timeh [sec], the electronic shutter speed is a value of N × Timeh [sec] (N is a natural number).

As described above, the conventional electronic camera incorporates logic called an exposure control system for performing exposure control and a clamp control system for determining the black level. It has been.
Now, as an index of the image quality of a video imaged by an electronic camera, there are phenomena such as a noise feeling within the frame and a phenomenon in which the luminance level of the image varies between frames. The former gives a rough feeling, and the latter is a phenomenon that causes a so-called flicker phenomenon. Both of these are important parameters that determine the quality of the image, and it can be said that quantifying the noise level and the flicker level is very important.

  Regarding the flicker phenomenon, for example, Japanese Patent Laid-Open No. 9-247550 discloses an example of a detection method thereof. This flicker detection method detects fluctuations in the fluorescent tube frequency of 60 Hz and 50 Hz. In Japanese Patent Laid-Open No. 9-247550, an average luminance level is detected for three fields at a shutter speed of 1/60 seconds, and the presence / absence of flicker is determined from the pattern. This is performed under the condition that the shutter speed is fixed.

  However, this flicker phenomenon may be caused by exposure control. That is, the exposure control calculates the evaluation value for exposure control from the luminance integration result of the light receiving area calculated by the photometry circuit (luminance integration circuit), and compares the value with the exposure target value set from the outside. In this method, the shutter speed of the image sensor and the gain of the amplifier are controlled so that both values are substantially the same. For this reason, when the exposure control system responds due to movement of the subject or noise, the shutter speed and the amplifier gain change, resulting in a phenomenon that the luminance level of the image fluctuates. This is the “flicker phenomenon resulting from exposure control”.

The flicker amount resulting from the exposure control cannot predict the frame rate at which the flicker phenomenon occurs. Therefore, as in the invention described in Japanese Patent Laid-Open No. 9-247550, the number of fixed fields can be reduced. I can't say that it should be detected.
Next, regarding the physical determination of the amount of noise in the image, it cannot be evaluated by simply applying a two-dimensional filter to the captured image. This is because the image filter output depends on the captured image. There is a method of judging from the difference between frames, but there are restrictions such as the necessity of a frame buffer and the fact that the camera and the subject do not move.
Japanese Patent Laid-Open No. 9-247550

As described above, conventionally, there has been no effective means for detecting the flicker level and the noise level used in video equipment such as an electronic camera.
SUMMARY OF THE INVENTION An object of the present invention is to provide a flicker level / noise level detector for use in video equipment such as an electronic camera, having a general-purpose, downsized and inexpensive configuration.

  In order to solve the above problems, a flicker level detector according to the present invention amplifies a signal imaged and output by an imaging means based on a predetermined gain, and then outputs a digital video signal output by A / D conversion. From the luminance metering means (for example, the luminance metering logic 13 in FIG. 1) for calculating the luminance evaluation value indicating the luminance of the entire captured image for each frame, and an AC signal from the output signal from the luminance metering means. AC signal extraction means for extracting, power calculation means for calculating the amount of power of the AC signal, and signal DC conversion means for converting the signal output from the power calculation means to DC It is characterized by.

  According to the above configuration, the flicker level is detected based on the luminance evaluation value in units of frames output from luminance metering logic (for example, luminance metering logic 13 in FIG. 8) that is originally provided in the video camera. Therefore, a versatile and low-cost flicker level detector can be realized. Furthermore, the flicker level can be detected without depending on the captured image (subject).

In the flicker level detector of the present invention, the AC signal extraction means is a digital HPF (for example, DETECTOR-HPF15 in FIG. 2), and the power calculation means is a digital absolute value circuit (for example, in FIG. 2). A full-wave rectifier 16), wherein the signal DC conversion means is a digital LPF (for example, DETECTOR-LPF 17 in FIG. 2).
According to the above configuration, it is possible to realize a flicker level detector with high accuracy while being low in cost.

The flicker level detector of the present invention is characterized in that the absolute value circuit is a full-wave rectifier.
According to the above configuration, for example, a flicker level detector with higher accuracy can be realized as compared with a half-wave rectifier having an absolute value circuit.
Further, the noise level detector of the present invention shields a part of the light receiving surface of the image pickup means and cuts out only the video signal of the shielded area (OB area or the like) (for example, FIG. 1). Cutting means 7), AC signal extracting means for extracting an AC signal from an output signal from the cutting means, power calculating means for calculating the amount of power of the AC signal, and output from the power calculating means And a signal DC converting means for converting the generated signal into DC.

According to the above configuration, since the noise level is detected from the OB region signal, a versatile and low-cost noise level detector can be realized. Furthermore, the noise level can be detected without depending on the captured image (subject).
In the noise level detector of the present invention, the AC signal extraction means is a digital HPF (for example, DETECTOR-HPF15 in FIG. 2), and the power calculation means is a digital absolute value circuit (for example, in FIG. 2). A full-wave rectifier 16), and the signal DC conversion means is a digital LPF (for example, DETECTOR-LPF 17 in FIG. 2).

According to the above configuration, a highly accurate noise level detector can be realized at a low cost.
In the noise level detector of the present invention, the absolute value circuit is a full-wave rectifier.
According to the above configuration, for example, a noise level detector with higher accuracy can be realized as compared with a half-wave rectifier having an absolute value circuit.

  Further, the flicker level / noise level detector of the present invention amplifies the signal picked up and output by the image pickup means based on a predetermined gain (for example, PGA4 in FIG. 1), and then performs A / D conversion (for example, Luminance metering means (for example, the luminance metering logic 13 in FIG. 1) for calculating, for each frame, a luminance evaluation value indicating the luminance of the entire captured image from the digital video signal output as ADC 5) in FIG. A part of the light receiving surface of the imaging unit is shielded from light, and a clipping unit (for example, the clipping unit 7 in FIG. 1) for extracting only the image signal of the shielded region, and a signal from the luminance photometric unit Alternatively, a selection unit (for example, selection unit 8 in FIG. 1) that selects and outputs one of the signals from the cutout unit, and an AC for extracting an AC signal from the output signal from the selection unit No. extraction means, a power computing means for computing the power of the AC signal, characterized in that a signal current means for direct current output signal from the power computing means.

According to the above configuration, the flicker level detector and the level detector of the noise level detector (for example, the level detector 9 in FIG. 1) are used in combination. Cost reduction can be realized. Furthermore, the flicker level and the noise level can be detected without depending on the captured image (subject).
In the flicker level / noise level detector of the present invention, the AC signal extraction means is a digital HPF (for example, DETECTOR-HPF15 in FIG. 2), and the power calculation means is a digital absolute value circuit (for example, The full-wave rectifier 16) of FIG. 2 is characterized in that the signal DC conversion means is a digital LPF (for example, DETECTOR-LPF 17 of FIG. 2).

According to the above configuration, a flicker level / noise level detector with high accuracy can be realized at low cost.
The flicker level / noise level detector of the present invention is characterized in that the absolute value circuit is a full-wave rectifier.
According to the above configuration, for example, it is possible to realize a flicker level / noise level detector with higher accuracy than the absolute value circuit of the half wave rectifier.

Embodiments of a flicker level / noise level detector according to the present invention will be described below with reference to the drawings. In this embodiment, the case where the flicker level detector and the noise level detector are integrated will be described as an example. However, each may be configured as a separate detector. .
(Embodiment of the Invention)
First, the configuration will be described.

FIG. 1 is a block diagram showing the configuration of a flicker level / noise level detector of the present invention. In FIG. 1, the flicker level / noise level detector includes a lens 1, an image sensor 2, an OB clamp circuit 3, a PGA (Programmable Gain Amp) 4, an ADC (Analog Digital Converter) 5, and a luminance photometry logic 13. And a cut-out means 7, a selection means 8, and a level detector 9.
(Flicker level detector)
First, the flicker level detector will be described.

In the present invention (flicker level detector), the luminance evaluation value of the frame calculated by the luminance photometry logic 13 is used for the purpose of exposure control and the like. The change amount of the luminance evaluation value is measured by the level detector 9 of the present invention.
As described above, FIG. 1 is configured to use both a noise level detector and a flicker level detector, which will be described later. When operating as a flicker level detector, the selection means 8 in FIG. 1 selects an output (luminance evaluation value) from the luminance photometry logic 13, and the output is input to the level detector. Yes.

FIG. 2 is a principle diagram of the flicker level / noise level detector of the present invention.
The circuit is composed of three blocks. The configuration includes a digital HPF (hereinafter referred to as DETECTOR_HPF) 15 for detecting the amount of change in luminance evaluation value in units of frames (AC component), and a digital absolute value circuit for calculating the power of this AC signal. (Hereinafter referred to as a full wave rectifier) 16 and a digital LPF (hereinafter referred to as DETECTOR_LPF) 17 for converting this signal into a direct current (DC). The full wave rectifier 16 may be a half wave rectifier.

The operation is based on the luminance evaluation value supplied from the luminance metering logic 13, taking out an AC signal indicating the amount of change at the DETECTOR_HPF 15, supplying the output to the full-wave rectifier 16, and making it a positive value only signal. The output is supplied to DETECTOR_LPF 17 and converted to direct current (DC), which is used as a detection result.
Next, an example of the detection result will be described.

When the present invention (flicker level detector) is used with and without exposure control, the following operation is performed.
First, the exposure control operation is performed. For example, when a slight luminance change or the like occurs in the captured image, the OB target value output from the error detector 11 and the luminance photometry logic 13 output. An error occurs in the evaluation value, and the shutter speed of the image sensor 2 and the gain of the PGA 4 change (see FIG. 8). Following this slight change in luminance, a flicker phenomenon occurs. Then, the flicker phenomenon resulting from the exposure control operation causes a change in the flicker level detection output, whereby the flicker phenomenon is detected in the present invention (level detector 9).

  Next, in the case where there is no exposure control operation, when the shutter speed of the image sensor 2 and the gain of the PGA 4 do not change (they remain fixed values), that is, the detected flicker detection amount depends on the subject or light source. For example, when the shutter speed is fixed to 1 frame (assumed to be 15 fps), the luminance change due to 60 Hz (60-15 × 4) of the light source is 0. Fluctuation does not occur, and a fluctuation of about 5 Hz (50-15 × 3) occurs with a 50 Hz light source. This 5 Hz change (five changes per second) occurs in the flicker level detection output, and the present invention (flicker level detector) detects the difference between the 60 and 50 Hz light sources.

Next, an embodiment designed in accordance with the gist of the present invention (flicker level detector) will be specifically described.
The flicker level detector of the present invention is composed of three blocks as described above (Table 1 below).

FIG. 3 is a circuit block diagram showing a specific example (IIR filter) of DETECTOR-HPF, and FIG. 4 is a circuit block diagram showing a specific example (IIR filter) of DETECTOR-LPF.
The DETECTOR-HPF in FIG. 3 adds the signal supplied from the selection means 8 in FIG. 1 and the signal supplied from the adder circuit 20b and outputs one frame of the signal supplied from the adder circuit 20a. The register 21a that is output after being delayed by a delay, the multiplier 22a that processes and outputs the signal supplied from the register 21a with a multiplication coefficient of -0.625, and the signal supplied from the register 21a is delayed by one frame. A register 21b for output, a multiplier 22b for processing and outputting the signal supplied from the register 21b with a multiplication factor of -0.5, and an adder circuit for adding and outputting the signals supplied from the multipliers 22a and 22b 20b, a multiplier 22c that processes and outputs the signal supplied from the register 21a with a multiplication coefficient of -0.375, an adder circuit 20a, and a register An adder circuit 20c that adds and outputs the signals supplied from 1b, a multiplier 22d that processes and outputs the signal supplied from the adder circuit 20c with a multiplication coefficient +0.1875, and a multiplier 22d and a multiplier 22c. 2 is added to the full-wave rectifier 16 of FIG.

Next, as for the operation, since this circuit (DETECTOR-HPF) is a known circuit, description thereof is omitted.
The DETECTOR-LPF in FIG. 4 adds the signal supplied from the full-wave rectifier 16 in FIG. 2 and the signal supplied from the adder circuit 23b, and outputs the signal supplied from the adder circuit 23a to the adder circuit 23a. A register 24a that is output after being delayed by a frame, a multiplier 25a that processes and outputs a signal supplied from the register 24a with a multiplication coefficient +0.125, and a signal supplied from the register 24a and the multiplier 25a are added. Output circuit 23e, register 24b that outputs the signal supplied from register 24a with a delay of one frame, and multiplication that outputs the signal supplied from register 21b with a multiplication coefficient of -0.4375. An adder circuit 23b, an adder circuit 23b for adding and outputting the signals supplied from the adder circuit 23e and the multiplier 25b, and a register 24a A multiplier 25c that processes and outputs the supplied signal with a multiplication factor of -0.25, an adder circuit 23c that adds and outputs the signals supplied from the adder circuit 23a and the register 24b, and an adder circuit 23c. A multiplier 25d that processes the supplied signal with a multiplication coefficient +0.125 and outputs it, and an adder circuit 23d that adds and outputs the signals supplied from the multiplier 25d and the multiplier 25c.

Similarly, since this circuit (DETECTOR-LPF) is also a known circuit, description thereof is omitted.
FIG. 5 is a diagram showing the theoretical frequency characteristics of DETECTOR-HPF, and FIG. 6 is a diagram showing the theoretical frequency characteristics of DETECTOR-LPF. The horizontal axis of each graph is a normalized sampling frequency of the electronic camera.

  Next, the overall characteristics (actual measurement values of the frequency characteristics of the flicker detector) when the flicker detector is actually made into a circuit are shown. As an input test signal for this purpose, a signal whose frequency changes (subtracts) from 0 Hz to fs / 2 [Hz] (fs is a sampling frequency of 15 Hz) is used. Further, the input frequency is changed at fs / 20 intervals, and the response to the signal is taken to obtain the overall characteristics of the flicker detector. The table below summarizes the overall characteristics of the detector as a gain (output value / input value) for each frequency.

As shown in the above table, since the gain varies depending on the frequency, flicker detection can be performed using this characteristic. That is, the gain in the state without flicker (near 0 to 1 Hz) is 0 times, the gain becomes 0 times or more when the flicker phenomenon occurs, the gain begins to appear when it exceeds 3.OHz, and the gain increases when it exceeds 4.5 Hz More than 1 time.
For example, the frequency response (gain) of fs / 2 is about 1.1 times, and when the input level to the flicker detector is 100 (/ 1024), it is detected as a level of 110/1024.

In addition, in the case of a 5 Hz luminance change caused by a 5 OHz light source, when the input level to the flicker detector is 100/1024, the gain is about 1.3 times, so the output is detected as 130/1024. . In this way, a flicker level detection output is obtained.
(Noise level detector)
Next, the noise level detector will be described.

FIG. 7 is a diagram showing the structure of the image sensor (light shielding area and light receiving area).
In an electronic camera, correction of the black level is usually performed in order to determine the brightness of imaging. For this reason, in an image sensor constituted by a collection of image sensors, light is shielded so that light does not enter the peripheral portion (see FIG. 5). Then, an average of the sensor outputs of the light-shielded area (light-shielding area 30) is calculated and used as a reference value, and the sensor output value of the non-shielded area (light-receiving area 31) is compared with the reference value. Thus, the brightness of the light receiving area is determined.

In the present invention (noise level detector), the noise level of the video signal from the light shielding area is determined.
In general, noise is mainly caused by noise from an image sensor, PGA4 noise, and ADC5 quantization noise. All three do not depend on the subject image. Therefore, the present invention (noise level detector) focused on the video signal of the light shielding area 30 that does not depend on the image. This is because a normal sensor (photodiode or the like) is also present in the light-shielding area 30 and its inherent noise is mixed.

  When FIG. 1 is operated as a noise level detector, the selection means 8 in the figure selects an OB region signal, and its output is input to the level detector 9. That is, out of the video signal from the image sensor 2, a signal corresponding to the sensor output of the light shielding area 30 is extracted by the cutting means 8. The extracted light shielding area signal is supplied to the level detector 9 described above. The detector consists of a digital HPF (DETECTOR-HPF) for detecting the noise (alternating current) component of the OB region signal, a digital full-wave rectifier for calculating the power of this alternating signal, and this signal as direct current ( The digital LPF (DETECTOR-LPF) for converting to DC) operates in the same manner as the flicker level detector described above. Note that, for both the digital HPF and the digital LPF, the delay register, which is a component, operates at the pixel rate (sampling frequency fs). The frequency characteristics are the same if the configuration and constants are the same.

In the present invention (noise level detector), the sampling frequency (fs) is the pixel rate in the overall frequency response characteristics of the noise level detector 9 (Table 2).
By the way, in the description of the flicker level detector, the circuit giving the frequency characteristics as shown in FIGS. 5 and 6 is shown, but the noise level can be detected by this circuit (the same circuit).
Therefore, according to the present invention (flicker level / noise level detector), the noise level detector and the flicker level detector can be used as the level detector 9 without any special conditions such as the flicker rate. A versatile flicker level / noise level detector can be realized. Further, the flicker level and the noise level can be detected without depending on the captured image (subject). Furthermore, since the flicker level and the noise level can be used with the same level detector (also used), the size and cost can be reduced.

  As described above, the electronic camera has been described as an example of the embodiment of the present invention, but the present invention is naturally applicable to a recording apparatus such as a television or a VTR.

It is the block diagram which showed the structure of the flicker level noise level detector of this invention. It is a principle diagram of the flicker level / noise level detector of the present invention. It is the circuit block diagram which showed the specific example (IIR filter) of DETECTOR-HPF. It is the circuit block diagram which showed the specific example (IIR filter) of DETECTOR-LPF. It is the figure which showed the theoretical frequency characteristic of DETECTOR-HPF. It is the figure which showed the theoretical frequency characteristic of DETECTOR-LPF. It is the figure which showed the structure (light-shielding area | region and light-receiving area | region) of an image sensor. It is the block diagram which showed the structure of the conventional electronic camera.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens, 2 Image sensor, 3 OB clamp circuit, 4 PGA (Programmable Gain Amp), 5 ADC (Analog Digital Converter), 7 Extraction means, 8 Selection means, 9 Level detector, 10 DAC (Digital Analog Converter), 11 Error Detector (ErrorDetect), 12 LPF (Low Pass Filter) 12, 13 Luminance Photometry Logic, 14 Luminance Control Logic, 15 DETECTOR-HPF, 16 Full-wave Rectifier, 17 DETECTOR-LPF, 20a, 20b, 20c, 20d, 23a , 23b, 23c, 23d, 23e Adder circuit, 21a, 21b, 24a, 24b Register (delay circuit), 22a, 22b, 22c, 22d, 25a, 25b, 25c, 25d Multiplier, 30 Light blocking area, 31 Light receiving area

Claims (9)

After the signal picked up and output by the image pickup means is amplified based on a predetermined gain, a luminance evaluation value indicating the luminance of the whole picked-up picked-up image is obtained from the digital video signal output after A / D conversion. Luminance metering means to calculate for each frame;
AC signal extraction means for extracting an AC signal from an output signal from the luminance photometry means;
Power calculating means for calculating the amount of power of the AC signal;
Signal directing means for directing the signal output from the power calculating means;
A flicker level detector comprising: 2. The flicker level according to claim 1, wherein the AC signal extraction means is a digital HPF, the power calculation means is a digital absolute value circuit, and the signal DC conversion means is a digital LPF. Detector. The flicker level detector according to claim 2, wherein the absolute value circuit is a full-wave rectifier. A part of the light-receiving surface of the image pickup unit is shielded from light, and a clipping unit that extracts only a video signal in the shielded region;
AC signal extraction means for extracting an AC signal from an output signal from the cutting means;
Power calculating means for calculating the amount of power of the AC signal;
Signal directing means for directing the signal output from the power calculating means;
A noise level detector comprising: 5. The noise level according to claim 4, wherein the AC signal extraction means is a digital HPF, the power calculation means is a digital absolute value circuit, and the signal DC conversion means is a digital LPF. Detector. The noise level detector according to claim 5, wherein the absolute value circuit is a full-wave rectifier. After a signal picked up and output by the image pickup means is amplified based on a predetermined gain, a luminance evaluation value indicating a luminance of the whole picked-up picked-up image is obtained from a digital video signal output after A / D conversion. Luminance metering means to calculate for each frame;
A part of the light receiving surface of the imaging unit is shielded from light, and a clipping unit that extracts only a video signal of the shielded region;
A selection means for selecting and outputting either the signal from the luminance photometry means or the signal from the clipping means;
AC signal extraction means for extracting an AC signal from an output signal from the selection means;
Power calculating means for calculating the amount of power of the AC signal;
Signal directing means for directing the signal output from the power calculating means;
A flicker level / noise level detector characterized by comprising: The flicker level according to claim 7, wherein the AC signal extraction means is a digital HPF, the power calculation means is a digital absolute value circuit, and the signal DC conversion means is a digital LPF.・ Noise level detector. 9. The flicker level / noise level detector according to claim 8, wherein the absolute value circuit is a full wave rectifier.

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